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Shattering the Myth of Fasting for Women: A Review of Female-Specific Responses to Fasting in the Literature

One of the more esoteric but much beloved tools in the paleo dieter’s tool-kit is intermittent fasting.

What is intermittent fasting? IF is the practice of maintaining overall caloric intake while consuming those calories in fewer meals or in reduced time windows throughout the day. The goal is to create conditions of fasting in the body, but not for extreme lengths of time.

Some examples of intermittent fast strategies include 10, 8, or 5 hour eating windows throughout the day, or perhaps eating just two meals each day: one in the morning, and one at night. The evolutionary premise — the argument that proponents of intermittent fasting make — is that humans evolved to optimize their health under less-than-optimal conditions. Fasting, they say, is a natural and perhaps even necessary part of being human. 

The modern-day scientific correlate appears promising, too:

Most people are nowadays aware that a calorie-restricted diet has the ability not just to decrease body weight but also to lengthen a human life.  Emerging research is beginning to show, however, that intermittent fasting is just as effective as calorie restriction in ensuring these health benefits! Amazingly enough, this happens without any of the psychological crippling side effects of cravings and food obsession that practictioners of calorie-restriction often experience.

Intermittent fasting, proponents say, also may benefit the fight against cancer, diabetes, and autoimmunity. Here is an excellent, up-to-date review of the “benefits” of fasting. It is wholly understandable that fasting is all the rage these days.

Sort of.

I have a specific interest in intermittent fasting because of what I have witnessed both in myself and in working with literally thousands of women in the PfW community.

Many women report to me (read more about that in this awesome book) that intermittent fasting causes sleeplessness, anxiety, and irregular periods, among many other symptoms hormone imbalance, such as cystic acne.

I have also personally experienced metabolic distress as a result of fasting, which is evidenced by my interest in hypocretin neurons. Hypocretin neurons have the ability to incite energetic wakefulness, and to prevent a person from falling asleep, in raction to the body detecting a “starved” state. Hypocretin neurons are one way in which intermittent fasting may dysregulate a woman’s normal hormonal function.

After my own bad experience with IF, I decided to investigate intermittent fasting. I looked into both a) the fasting literature that paleo fasting advocates refer to, and b) the literature that exists out in the metabolic and reproductive research archives.

Intermittent fasting and women: problems in paleo

What I found is that the research articles cited by Mark’s Daily Apple (and others),  focus on health benefits such as cancer-fighting properties, insulin sensitivity, and immune function.

However. I was struck by what seemed like an egregious sex-based oversight in that MDA post I linked to above.  MDA cites this article as a “great overview” of the health benefits of intermittent fasting. This startled me because the article MDA cited was for me one of the strongest proponents of sex-specific differences in response to fasting.

Sex differences were relevant in two striking areas:

1) women in studies covered by the review did not experience increased insulin sensitivity with IF regimes and

2) women actually experienced a decrease in glucose tolerance. 

These two phenomena mean that women’s metabolisms suffered from IF. The men’s metabolisms on the other hand improved with IF across the board.  ecall that the review was reported by MDA as “a great overview of benefits [of IF].”

Secondly, in another fasting post at MDA, of which there are many, the health benefits of fasting are listed and reviewed, but the sex-specific aspects of the hormonal response go unmentioned, and reproduction/fertility/menstrual health isn’t mentioned at all.

This is not to say that Mark is not attentive to who should and who should not be fasting.  He knows very well and cautions people against the dangers of fasting while stressed. Still, the mere fact of being more sensitive to fasting simply by being a woman is, I would assert, pretty important for a woman who is contemplating or already practicing IF.

This goes nearly unmentioned in the blogosphere.

Intermittent fasting and women: problems in the literature

Beyond reporting biases in the blogosphere, there remains an even greater problem of a significant testing bias in the fasting literature. Searching “men” + “intermittent fasting” in a Harvard article database yields 71 peer-reviewed articles. Searching “women” yields 13, none of which are a) solely about women b) controlled studies or c) about more than body weight or cardiovascular benefits.

The animal studies are more equitable, but also a bit less applicable to human studies.

 It is well-known in both the research and the nutritional communities that caloric restriction is horrible for female reproductive health. This is not news. There is an infertility condition – called hypothalamic amenorrhea – that millions of women suffer from due to being overly restrictive. But what of fasting?

Intermittent fasting and women: should women fast?

The few studies that exist point towards no.

It is not definitive, since the literature is so sparse, and it necessarily differs for women who are overweight versus normal weight (and who have different genetic makeups), but when it comes to hormones, women of reproductive age may do well to err on the side of caution with fasting.

What follows first is a brief review of what can be gleaned in sex-specific responses to fasting in animal studies. Afterwards I talk about what has been concluded by the few relevant human studies.


Mice and Rats

First up is a study that demonstrates the hippocampal  changes of calorie restriction and intermittent fasting for both male and female rats.  In this study, they do alternate day fasting, which entails free eating on one day and a fast day on the next.

The study found that brain states while fasting were different for male and female rats.  For male rats the change in hippocampus size, hippocampal gene expression, and ambulatory behavior was the same no matter what kind of restricted diet they were on – but for female rats, the degree of change in brain chemistry and in behavior was directly proportional to degree of calorie intake, demonstrating the unique sensitivity of female rats to the starvation response.

” The organization of the females’ response to the energy restricted diets is suggestive of some underlying mechanism that may allow for an organized, pre-programmed, response to enhance survival in times of food scarcity. Comparatively, the males’ genetic response was less specific, suggesting that the males respond to a general stressor but they seem to lack the ability to discriminate between a high energy and low energy stressor.”

Moreover, “IF down-regulated many gene pathways in males including those involved in protein degradation and apoptosis, but up-regulated many gene pathways in females including those involved in cellular energy metabolism (glycolysis, gluconeogenesis, pentose phosphate pathway, electron transport and PGC1-α), cell cycle regulation and protein deacetylation.”  In this study, both male and female rats gained small amounts of weight on IF diets.


For female rats, even in the most innocuous form of restriction–intermittent fasting–significant physiological changes take place.  Male rats do not experience as dramatic hippocampal and general brain chemistry change as female rats do, and their behaviors, specifically their cognition and their dirunal and nocturnal activity, do not change.  

Female rats, on the other hand, “masculinize.”  They stop ovulating and menstruating.  They become hyper-alert, have better memories, and are more energetic during the periods in which they are supposed to be sleep.  Theoretically, according to these researchers, this is an adaptive response to starvation.  The more the female rats need calories– or at least the more their bodies detect a “starvation” state– the more they develop traits that will help them find food.  They get smart, they get energetic, they get active, and they stop sleeping.

In a follow-up study conducted by the same researchers who explored the masculinzation of female rats, the researchers analyzed the gonadal transcription of male and female rats subjected to IF regimes.

This study found that male reproductivity up-regulates in response to metabolic stress. Female reproductivity down-regulates.  

Completely opposite to the female rats becoming infertile while fasting, male rats become more fertile. In the researchers’ own words: “our data show that at the level of gonadal gene responses, the male rats on the IF regime adapt to their environment in a manner that is expected to increase the probability of eventual fertilization of females that the males predict are likely to be sub-fertile due to their perception of a food deficient environment.”


In the final relevant IF rat study I could find, researchers subjected rats to the same diets– to 20 and 40 percent Calorie-Restricted (CR) diets, as well as to alternate-day fasting diets, and monitored them over the long term for hormonal responses.  The results were striking.  Below is the abstract in full because it’s so powerful:

Females and males typically play different roles in survival of the species and would be expected to respond differently to food scarcity or excess. To elucidate the physiological basis of sex differences in responses to energy intake, we maintained groups of male and female rats for 6 months on diets with usual, reduced [20% and 40% caloric restriction (CR), and intermittent fasting (IF)], or elevated (high-fat/high-glucose) energy levels and measured multiple physiological variables related to reproduction, energy metabolism, and behavior.

In response to 40% CR, females became emaciated, ceased cycling, underwent endocrine masculinization, exhibited a heightened stress response, increased their spontaneous activity, improved their learning and memory, and maintained elevated levels of circulating brain-derived neurotrophic factor. In contrast, males on 40% CR maintained a higher body weight than the 40% CR females and did not change their activity levels as significantly as the 40% CR females. Additionally, there was no significant change in the cognitive ability of the males on the 40% CR diet.

Males and females exhibited similar responses of circulating lipids (cholesterols/triglycerides) and energy-regulating hormones (insulin, leptin, adiponectin, ghrelin) to energy restriction, with the changes being quantitatively greater in males. The high-fat/high-glucose diet had no significant effects on most variables measured but adversely affected the reproductive cycle in females. Heightened cognition and motor activity, combined with reproductive shutdown, in females may maximize the probability of their survival during periods of energy scarcity and may be an evolutionary basis for the vulnerability of women to anorexia nervosa.

They also found this:

The weight of the adrenal gland was similar in rats on all diets; however, when normalized to body weight CR and IF diets caused a relative increase in adrenal size, the magnitude of which was greater in females, compared with males. 

And this:

The testicular weight was unaffected by any of the diets. In contrast, both CR diets and the IF diet caused a decrease in the size of the ovaries.

And this, bearing in mind that “daytime” for nocturnal rats is “nighttime” for humans:

The daytime activity of females was doubled in response to IF, whereas the IF diet did not affect the activity level of males. Nighttime activity levels of males and females were unaffected by dietary energy restriction.

And this:

 Uterine activity was monitored daily with vaginal smear tests; cyclicity was scored as regular, irregular, or absent. The mild energy-restriction diets (20% CR and IF) significantly increased the proportion of animals displaying irregular cycling patterns, whereas the 40% CR animals displayed an almost complete loss of estrous cyclicity.

And this:

 In males, corticosterone levels were elevated only in response to the 40% CR diet, whereas in females corticosterone levels were significantly elevated in response to all three energy-restriction diets, suggesting a relative hyperactivation in females of the adrenal stress response to reduced energy availability.

For lipids, all the rats did well: “Collectively, these data suggest that atherogenic profiles of both males and females are improved by dietary energy restriction.”  Interestingly, too, as they pointed out in the abstract, human females also perform cognitively much “better” (memory and alertness) on CR and IF diets than on normal feeding schedules.

There are of course some caveats to this study: A) They are rats.  B) They are somewhat “metabolically morbid” rats, which may make them more susceptible to disease.  C) The rats were allowed to eat ad libitum on the IF days, but they simply did not meet their caloric requirements this way.  So while it is a somewhat natural form of IF, it is still calorically reduced, such that that must be taken into account when gasping in horror at the hormonal responses of IF-ing female rats.


The Few Human Studies

I mentioned above that through the same review that MDA used as a “great overview” of IF benefits for all sexes, I found harmful metabolic effects for women subjected to alternate-day fasting regimes.

This is the study:

Heilbronn et al found that with IF, insulin sensitivity improved in men (21 participants) but not in women (20 participants): after three weeks of alternate day fasting, insulin response to a test meal was reduced in men. Women experienced no significant change. “It is interesting that this effect on insulin sensitivity occurred only in male subjects,” they report.

With respect to other health markers female health actually declined, specifically with respect to glucose tolerance:

“Another diabetes risk factor that has shown a sex-specific effect is glucose tolerance. After 3 weeks of ADF, women but not men had an increase in the area under the glucose curve. This unfavorable effect on glucose tolerance in women, accompanied by an apparent lack of an effect on insulin sensitivity, suggests that short-term ADF may be more beneficial in men than in women in reducing type 2 diabetes risk. ”  The opening line of their discussion reads: “Alternate day fasting may adversely affect glucose tolerance in nonobese women but not in nonobese men.”

In a follow up study,  Heibron et. al studied the effects of alternate-day fasting on cardiovascular risk.  When human subjects fasted on alternate days for another three week period, circulating concentrations of HDL cholesterol increased, whereas triacylglycerol concentrations decreased.  This is a good thing.  However, the shifts in lipid concentrations were shown to be sex specific: ie, only the women had an increase in HDL-cholesterol concentrations, and only the men had a decrease in triacylglycerol concentrations.

The most recent review of IF agrees with my conclusion: sex-specific differences in metabolism exist and need to be studied further.

This study of alternate day fasting included 12 women and 4 men.   In eight weeks, body weight decreased by about 10 pounds, and body fat percentage decreased from 45 to 42.  Blood pressure decreased, total cholesterol, LDL cholesterol, and traicylglycerol decreased.  These people were significantly obese, which limits the results of this study to an obese population.  However, “perimenopausal women were excluded from the study, and postmenopausal women (absence of menses for >2 y) were required to maintain their current hormone replacement therapy regimen for the duration of the study.”  (Their words, my emphasis)


The one, big study of intermittent fasting conducted on men and women looked at differences between isocaloric feeding schedules: 3 meals/day feeding versus 1 meal/day.

The study focused on body weight composition, blood pressure, and body temperature in subjects.  Subjects were fed isocalorically either one meal each day or three meals each day.  All subjects were between 40 and 50 years old (excluding women of reproductive age), and between BMIs of 18 and 25.  They ate, so far as I can tell, a healthy diet with 35 percent fat, PUFA < MUFA < SFA.   Only 15 of the original 69 completed the study (which goes to show just how fun everyone thought fasting was).  As for the results,

“Systolic and diastolic blood pressures were significantly lowered by ≈6% during the period when subjects were consuming 3 meals/d than when they were consuming 1 meal/d.  No significant differences in heart rate and body temperature were observed between the 2 diet regimens.    Hunger was enormously larger in the one meal/day than in the three meals/day group.  “The 1 meal/d diet was significantly higher for hunger (P = 0.003), desire to eat (P = 0.004), and prospective consumption (P = 0.006) than was the 3 meals/d diet. Feelings of fullness were significantly (P = 0.001) lower in the 1 meal/d than in the 3 meals/diet.”   Body weight dropped only four pounds after several months.  Cortisol dropped, but  Total, LDL, and HDL cholesterol were 11.7%, 16.8%, and 8.4% higher, respectively, in subjects consuming 1 meal/d than in those consuming 3 meals/d.

In sum: patients on the one meal/day regiment were unhappy, hungry, lost a little bit of weight, increased cholesterol.  This was a small sample, included somewhat menopausal women, and all people of normal body weight.

Intermittent fasting and women: In conclusion

All that being said, that’s it. That’s all that exists! Women don’t have much to go on.

There are a few rodent studies. They found that when alternate-day fasting,female rats and found significant negative hormonal changes occurring in the females.

There are even fewer human studies. Human studies on alternate day fasting have not been conducted on women of reproductive age at all, nor have any studies analyzed reproductive responses to fasting.  

Moreover, the few studies that have been conducted on non-obese women have demonstrated that their metabolic responses are not nearly as robust as those of men, and may in fact be antagonistic to their health.

This post has focused on sex-specific responses to fasting. Another important distinction to make is between different body weights. Overweight and obese patients appear to experience significant improvements with IF regimes, but normal weight patients do not show the same across-the-board benefits. For women this may be a particularly sensitive issue. Overweight women may experience metabolic benefits, whereas normal weight women do not. I suspect that that may roughly be the case, but who knows. Honestly, no one at this point.

The practical solution, then, I believe, is to look at options, to be honest about priorities, and to listen to one’s body with awareness and love.

Is fasting worth trying if a woman is overweight and trying to improve her metabolic markers, and so far hasn’t had much success?  Perhaps.  Should it be undertaken if a woman is of normal weight?   What if she is a light sleeper?  What if her periods begin to dysregulate?  Or stop?   What if she starts getting acne, getting a stronger appetite, or losing her appetite altogether?  These things happen, and I see them in women who fast and contact me time and time again.

We women (people!) should be honest with ourselves about our priorities, and act constantly with our mental and physical health foremost in our minds.  All women are different. But the literature is so sparse in this area that we cannot make any real statements or predictions about the effects of fasting, other than that we just don’t know, and that we should continue to emphasize the centrality of awareness, caution, and loving nourishment in moving forward.



IF is one realm in which the female body has unique characteristics and needs that demand attention. There are boatloads of others. If you’re interested in reading about the collective set of them and learning how to optimize female skin, weight loss, and hormone balance, for a few examples, you could do worse than my best-selling book, Sexy by Nature, here.



And that’s a wrap! What do you think?


So, just as a heads up - some links above may be my affiliate links, which means I get a small commission if you click on it and make a purchase. Doing so is no additional cost to you, but helps me tremendously. Your support is SO greatly appreciated, so thank you in advance if you choose to do so. Check out my entire disclosure to know exactly how things work.

Managing director of Paleo for Women and author of Sexy by Nature.


  1. Thank you, thank you, THANK YOU for this! I’ve had a sneaking suspicion now for months that so much of the IF hype is skewed towards males. My fiance swears by only eating two meals a day, whereas if I skip a high-protein breakfast, my day is effed. IF has never worked for me, and it’s good to find a little evidence as to why.

    • Thank you for your very informative article.
      I am an active, overweight (approx. 5-8kgs) but otherwise healthy 37 yo woman. I have been practising IF for 3 months by only having 1 meal a day twice a week. I have lost a modest amount of weight only but my skin is much improved (previously very prone to acne). So far I have had no cycle issues but if I want to have children in the future I may change my mind! Perhaps restricting IF to twice weekly limits some of the more serious metabolic side effects?
      (In the name of science, I would happily revert to my previous wicked ways for a few months, have some blood tests and then IF for an appropriate time then get tested again… if anyone is interested in a study group in the making amoungst these bloggers!)

    • To me IF is the way to go, I’m 22 and on my weight and I’ve always forced myself to eat breakfast until I just stopped, I’m never ever hungry in the mornings I just cant manage to eat that early. I usualy have to big meals and a coffe in between them. I hate snacking I rather have two huge meals that multiple small ones. Also if I have breakfast I feel more hungry during the day, idk why but if I eat something in the morning I feel super hungry for the rest of the day.

      I always try to listen to my body (eat when I’m hungry stop when I’m full) and skipping breaksfast seems to be whats best for my body, I’m going to keep doing that until I see some kind of adverse result

    • I would like to thank you also. I am a normal weight female and very active in the gym. I tried IF and I felt miserable. I have such a hard time function which lead me to this site. I kept trying to convince myself that this is going to take willpower and I just have to get through the training stage. I don’t even know if it’s worth continuing after reading this article. I think that I will stop because it’s simply ruining my workload. I can try again later in life when there’s better research geared towards normal weight, active females. However now I know that eating breakfast is not an absolute and we can beat Market America if we choose to.

  2. Pingback: Paleo Pepper » Blog Archive » Shattering the myth of fasting for women: A review of sex-specific responses to fasting in the literature

  3. Thank you again! With all the IFing (predominantly male led as well) devotees, I have been perplexed by my inability to pull it off as a lady. Oh sure I can go without eating no prob. But if I want to have a period and not grow a damn mustache then I better eat a few small balanced meals and not just one a day, or every other day as some do.

    I have a great exchange with “grace” who is DR. BG from the Animalpharm blog on paleohacks http://paleohacks.com/questions/100365/ifing-ketosis-stressing-adrenals-cortisol-fat-storage/100383#100383 a while back about fasting. I also noted that one study showed that fasting can cause a “high” in females which can be addicting to some. Perhaps this illustrates the slippery slope of anorexia?

    • Wow, thanks for that tidbit about the “high”. For a while, I was IFing through my morning with only coffee, which was great for a while, especially with creativity while writing. Until it wasn’t anymore and now my adrenals are down. I didn’t find it addicting, per se, but the effects were interesting and helpful enough to make me think it was a good combo. But alas, all good things must come to an end.

      • Yes, that is crucial, and I think I might give it a post of its own. We talk so much about listening to our bodies– I know I do!– but sometimes physical intuition is not our greatest tool (versus, say, science), especially considering how subjective we all are. I actually wrote a post on this at my old blog probably more than a year ago now. JStanton over at http://gnolls.org also recently wrote about it.

      • Thank you for this post and thread. I’m currently stuck in this bad habit. I always used to start my morning with a high-protein, high-fat, vegetarian breakfast (usually: spinach, avocado, and loads of sunflower seeds, dressed with EVOO and Himalayan salt) and had great results with that. Lately I’ve been getting busy in the mornings, nursing coffee for a few hours until I realize I’ve missed breakfast but it’s not quite time for lunch yet, so holding out a couple more hours. As a result I’m “IFing through my morning with only coffee” and I keep telling myself every night, “Tomorrow I’m going to eat a real breakfast!” and then somehow every morning it’s suddenly 11:30 and I finished my coffee an hour ago and still haven’t gotten up from my desk to make breakfast. It’s like I get on this caffeine-fueled productivity high which is probably creating a positive reward association even though part of me is trying to stop doing it!

    • That is very interesting. When I was in the throes of anorexia, I would feel energized, light, all these crazy things when I’d go days without eating. Like an addiction, I always felt I needed to fast more to feel that good.

      In the meantime, my hair was falling out, I was growing MORE hair on my arms and legs, I was cranky and evasive with people without realizing it, and of course, damaging my metabolism.

      I research the IF quite a bit because, trying to lose weight in a healthy manner, I was quick to snap at people who suggested starving when I would bring up my comments. But now I’m wondering if I shouldn’t have stepped down, since they all tended to be men!

      • Exactly!! I know what you mean, when I was anorexic I did feel the high of not eating, you feel super awake and aware and with lots of energy despite being very weak. I beat that and started to get healthy and then about a year later I heard about IF. When I tried it I got the same high off it, which I really enjoyed but it also made me so anxious because I felt I was slipping back into old habits, it all seemed too familiar… Also, I lost my period for a few months and it came back the week after I started eating normally again.
        I know it works for some but I wouldn’t advise it to
        1. Anyone (man or woman) that has had an eating disorder
        2. Any pre-menopausal women, there has been too many cases of hormonal imbalances due to IF

    • YES. I have struggled with very restrictive eating in the past, and it can be super addictive…especially when you are not thinking straight (on the high). If I go a certain amount of time without eating, its like this idea pops into my head that I’ve already been “x” hours without food, so what is 5 more? …vry scary!! Also i have had a lot of trouble sleeping with IF 🙁

    • Just came across this blog. I started IF in February 2013 doing the 8 hour diet. Found it easy, I lost 6 pounds very quickly but became underweight. Lost my period completely. Have started eating normally again for 2 months and my period has returned! True about the high though, I found IF addictive and would get so anxious if I went even 1 minute over my ‘allowed’ eating time. Never again.

      • I’m going through the exact same thing. I dropped below a healthy BMI, I haven’t had a period for 2 years, I tried everything to get it back, I’ve put on a lot of weight (more than I lost) and still no sign of a period 🙁 although, I still struggle with letting go of IF, i’m so used to having nothing but coffee upon waking and I suppose it feels normal because my bf does it too. I just get this anxiety that I’m going to make myself even more overweight if I start eating breakfast :<

        • Hi . To address the topic of your period you should go see an ob/gyn because the same thing happened to me. the ob/gyn told me that some sort of stress ( intermittent fasting) had turned off my ovaries from working, and they havent turned back on. kinda like a computer.

  4. Thank you for this article. I tried fasting when I was participating in disordered eating- but have since decided to lay off for awhile- and this is further evidence to continue to forgo fasting- especially while we are trying to conceive! Thank you for all that you do.

  5. Hi, good article. I practice IF. 2 meals a day usually, fasting between about 8.30 at night and 11.30am. Sometimes fast time is not so long, sometimes it’s longer. Sometimes I have b’fast. Sometimes I snack. I try to listen to my body in that regard. I feel this suits my natural instincts re. eating. I have never been hungry in the morning but at times in the past (thinking I was doing my health a disservice) I forced myself to eat breakfast. It never felt right to me. I notice that the days I eat b’fast now, the hungrier I am all day. When I don’t, my appetite is stable. I am content. I am not overweight so weight loss is not an issue. I sleep fine. My periods are irregular – but they ALWAYS have been. I can’t say things have become worse since commencing IF. I have a big endometrioma on one ovary, and the other is polycystic (for 14 years). So that would be why my periods are irregular. Things are a lot better since going Paleo. I’ve had a child in the past, with these problems, with no hassle. I think it goes to show that all women are different. I can’t say I feel a lot better since specifically starting IF, but I certainly don’t feel worse, and this way of eating seems to suit me psychologically and physically – at least in terms of appetite rhythms. Women should listen to their own bodies. Don’t be scared to try, but also don’t be scared to change and adapt if this doesn’t suit you. Everyone’s different.

    • When you eat breakfast, what do you usually eat? I’ve found that high-carbohydrate meals in the morning make me hungrier all day and also lead to a crash in the afternoon. I’m much less sensitive to carbs at lunch and dinner than I am at breakfast, but ironically most traditional breakfast foods are high in sugar and starch (pancakes/waffles, cereal, fruit, toast, juice). I do better with breakfast than without, but it has to be a very low-sugar, high-fat, high-protein breakfast to give me lasting energy without making me hungrier throughout the day. As I mentioned above my favorite breakfast is a small salad of spinach or other greens with several teaspoons of sunflower seeds for protein, 1/2 or 1 whole avocado and 1-2 tablespoons of EVOO for healthy fat, and a bit of Himalayan salt for flavor and minerals. A lot of people find it incredibly strange that I eat salad for breakfast, but traditional breakfast foods just don’t work for me! Which echoes what you say: we should honor our bodies by listening to them and adapting to their needs.

      • Protein! I always have protein for breakfast. And keep my carbs to later in the day, in order to maximize my insulin sensitivity.

        Right. Eat all the salad you want! More power to you. And it breakfast really does mess you up, even if its a protein or fat breakfast, then go ahead and put it off until you feel comfortable eating… whatever feels best for you.

        • I just recently read, to always eat protein first at all meals. That protein starts the digestion process. Then eat your veggies last. Restaurants have it backwards by serving salads first. Except in Italy they serve vegetables last.

          • Women in France are usually thin and healthy, and it is the custom there to always have salad last….maybe they have known something we didn’t?

    • i too have no appetite in the mornings- though i try. if i have a high protein breakfast (before 10 am) i hurt, have indigestion, and have food cravings and mood swings for the rest of the day. carbs just put me back to sleep. juicing green veggies is my favorite breakfast and jump starts my appetite for sure. if i have a cucumber/kale/celery/green juice, i get hungrier much faster and usually need my first meal before 11.

      i do well with 2 meals a day, maybe a snack, no grains, but not low carb. especially in the later meal, i need more carbs or a paleo treat like almond flour cookies. i sleep extremely well, have regular cycles, healthy babies, great breastmilk supply, and a good muscular body weight. i think i have higher levels of testosterone than many women (my sister has been tested, and the women in my family have a pattern of that) and probably androgen as well, which could make IF’ing work better for me. no caffeine, no cravings, and very stable blood sugar at 75 fasting and 72 post meal. i didn’t know i was IF’ing until i started reading about it, and it helped me stop fighting my natural urges and figure out what worked best for my body, which as tasty as the eggs and veggies the kids eat are, is NOT that! at 5’4″ and 130, i’m not tiny, nor large, and have a good fat layer, good muscles, and don’t feel like i need to lose any weight by fasting.

      • Hey Mama, are you eating all your meals within an 8 hour period of the day (IF ing every day)?

      • Same here! I had no idea what IF was until like 2 hours ago. I’ve just never liked eating breakfast, it makes me feel sluggish and hungrier during the day (except when I was pregnant, then I absolutely HAD to have my eggs and whole-wheat toast). I’ve always felt guilty about skipping “the most important meal of the day,” but physically I’m in excellent health and with none of the complaints mentioned in this research (thank goodness)… My periods were never regular–so I guess it explains that, but I didn’t have any trouble at all conceiving. To be fair, thanks to the irregular periods, I didn’t know I’d conceived until I was almost through my first trimester!
        Now I feel like I finally have a name for my natural eating rhythms. Count me a member of the “no breakfast” club!

    • BINGO Lara! Every BODY is different! I agree when I eat breakfast, I am more hungry throughout the day. I jhave recently started IFing and I feel great and I have found that I sleep better! I think it is because I am getting my calories later in the day and I actually feel full and satisfied rather then hungry and waiting until my next meal.

      • Same here, I have never had any of the problems mentioned with IFing – periods remain regular, no anxiety or difficulty sleeping… I was quite surprised to read about these problems, TBH!

    • I just started IF about a week ago so this is very new to me and all of the comments are very interesting and are steering me away from wanting to do it. I think it is true that everyone is different and I will just have to see how I feel. It’s nice to hear it’s been positive for you!

    • I can relate to your post because I do it similarly, Lara. I usually try to keep my eating in an 8h window (10am – 6pm). Sometimes my fast time is longer, other times shorter. Sometimes I eat snacks, other times I keep it simple with 2 meals a day. Sometimes I keep it low-carb, other times, I have to have a little bit of ice-cream or chocolate. I always try to listen to my body. What I always do is have my morning coffee with coconut milk and heavy cream. It makes me happy and keeps me non-hungry for a while. I cannot, however, go without having anything in the morning. I am not overweight and my period is regular, never had any issues. No acne either. I like this way of eating because it keeps my weight stable. If I eat all the time, I gain weight easily. I do best if I don’t eat after 6pm. If I have a “meal” for breakfast (low-carb), it makes me hungry and I want to eat all day long! My coconut milk coffee is a perfect breakfast for me. What’s interesting about my hormones is the fact that I have a slightly higher level of testosterone – but no problems with body hair, acne, etc. Perhaps, that’s why I react okay to IF…I don’t know…Overall, IF works for me , but I always adjust it to the current needs of my body.

    • I totally agree, we should listen to our bodies… If the communication between our body and mind is still good, unfortunately it’s not always the case, some people forces themselves into stupid diets and other things. My body-mind communication is nice so I use the signs of my body if it’s about food. There are contradicting articles (it’s hard for someone who isn’t an expert’ I researched a lot and while I think I found some answers, many questions remained) and individual differences.
      Till recently I never knew not eating for 16 hours a day is IF… It was perfectly natural to me. I eat when I’m hungry but I’m not hungry after I wake up. When I ate the meal I called breakfast in my adult life, it was at least at 11am 🙂 Earlier breakfast would have felt force feeding and I just got hungry. I could test it in very low-carb situations. It’s the same. Breakfast isn’t for me, physically or mentally.
      Today I did 20/4 IF but it’s usually something closer to 18/6. I’ve read somewhere too long fasts aren’t for women either… But it’s what comes naturally. Okay, I actually want to do it this way because it’s so better this way but I eat when I’m hungry, it’s very, very basic for me.
      Losing weight isn’t automatic, I could eat over 2000 calories in a single hour if I need to I guess, it’s really no big deal using my fatty food… Well, I would need preparations for that but eating my calories in 4-8 hours? I need to make efforts not to eat way more than 2000 on some days! Long-term keto changes this, I eat at a little deficit then 🙂 (Rarely, even under my maintenance level according to calculators. Fortunately, they are wrong in my case.) My body and mind rejects the idea of eating too little.
      I’m so not the typical dieter… But keto and IF seems to work for me just like for several other people. Not so magically regarding weight-loss, the combined efforts of them can’t garantee that but they make it possible, pleasant and easy.

      I’m very sorry for all lab rats. Poor things couldn’t even eat enough. Not the worst things that could happen to them though.

      • I was doing keto for a year and a half (using Bulletproof IF) before I started having problems, and then it was like everything went into reverse. I started gaining weight, having uncontrollable cravings, having menstrual irregularities and acne, and just overall feeling lousy. I wish I had just cycled up my carbs more often, especially using fruits, starchy vegetables and potatoes – toward the end of my keto days, when the cravings started, I tended to have more “cheat” days eating things like chips and gluten-free crackers, which had not been part of my normal diet for a very long time. Before I knew it I was totally out of control, thyroid and reproductive system completely out of whack. But up until those last couple of months, it seemed like it was working like a charm. So to anyone reading this post and still considering keto/IF, or if you’ve been doing it for what seems like a long time successfully, just be aware that it may not work forever. I imagine a lot of it depends on things like starting leptin levels (I started my period at 10 years old, which is a pretty good indicator of a leptin imbalance based on the reading I’ve done), but I really thought I could do it forever and continue to get the same results. I’ve tried to re-enter keto a few times with miserable results. For now I am eating a high-calorie, nutrient-dense diet and attempting to maintain my weight for the first time in my life, despite a BMI of 32. But looking back it seems like I’ve always been either gaining or losing since I was about twelve years old, and that is no way to live.

  6. wow! thank you so much for this information. IF’ing is so tempting – so many in this paleosphere rave about its benefits and really urge everyone to give it a try. ive thought about it and have come very close, but there has always been some mysterious gut-sense that it just wouldnt be healthy for me.
    for the most part, i think “paleo” is learning to trust your instincts and to do what feel most natural to you as an individual. im glad i read this today – a great reminder of why i should stop trying to micromanage my humanness and just trust my own instincts more often 🙂

    • “ive thought about it and have come very close, but there has always been some mysterious gut-sense that it just wouldnt be healthy for me.”

      I have felt the same way, the blogs and fitness experts in the paleo field rave about it, it’s the next step in, really, “perfecting” your body’s responses/health….and yet when I’ve tried it I always felt I must be doing something wrong because it really felt wrong, like I was trying to force something that wasn’t meant to be done.

      Never did it long enough to experience any actual symptoms, just a feeling like my body didn’t want it.

      There is so, SO Much to be said for listening to that quiet voice inside!

  7. This is pure gold. Thank you Stef, this one’s been long awaited, after experimenting myself with daily 14-18hr fasting and challenging resistance training- I turned my once smoothly-operating endocrine system onto it’s head. Thanks for doing the hard work: the research. 🙂

    • Hi There! Just wondering if your “once smoothly-operating endocrine system” has returned? I too got myself way off kilter with IF. I’m following Diana Schwarzbein’s (endocrinologist) lead and eating balanced meals throughout the day. The Transition is her book & she’s coming out with another soon which is entitled “Survival of the Smartest”. She seems to believe that Paleo & IF trends are worse than the “no fat” trend of the 80’s/90’s. I’m hoping my sleep will return to normal. I miss it. If you have any tips for endocrine-system repair, I’d love to hear. Wishing well

      • I personally continue to heal the more and more regularly I eat and the more I am able to convince myself to eat plenty of fat and carbs both 🙂

  8. Thank you for another great and very informative article! I think it is about time that we see that what might be good for men is not necessarily a good idea for women! Thanks for your work!

  9. Like Lara I too practice IF.
    6 days a week I go about 16 hours fasting. Which means depending on what time I last eat, usually 7pm at night, I will eat 16 hours later. So I usually eat around 11am.
    I eat a Paleo diet, but with a fairly high percent of fat – about 60-70%, which would come from avocado, coconut oil & cream, fat from meat and lots of eggs.
    Also like Lara I find this helps my appetite. The days I am fasting I am not overly hungry, and on the days I eat, I am generally hungrier.
    I am 43, not overweight and have finished having kids. My periods are regular. My sleep is good, but perhaps not perfect, though I don’t believe that is due to IFing, I could be wrong though.
    I have also wondered why most articles on IF are written mainly from the male perspective. In fact I find it very frustrating as I try to do as much research as i can on anything I do before trying it.
    But anyway this is my perspective and, for me I believe IFing works well.

    • Thanks for sharing Rebecca! The whole point of this post isn’t to tell anyone they are doing it wrong, but rather that they should listen to their bodies above all else. Glad to see you found something that works for you 🙂

  10. Hi! I am loving your blog and all the research you are doing. I have PCOS myself, and went on paleo to cure it, and the biggest thing that I came out with was furthered orthorexia. I feel like I have learned a lot from Paleo about nutrition, but the initial carb restriction really screwed me up, mentally and physically! Glad to see you are supporting carbs and not fasting. Because I need need need food choice freedom in order to eat intuitively (I have tried “intuitive eating paleo”… mind won’t let it work) I am not doing or pushing pure paleo on my blog. But I really appreciate all the research you are doing, and all the articles you are putting out. I will definitely keep reading!

    Keep it up!

    • Thank you Caroline. Really, I can’t tell you how much that means to me. Moreover, I really can’t tell you how much I empathize, and how excited I am about your future. You’re going to do great with your new endeavor. Prioritize your happiness and your freedom, and I think your body will fall right in line 🙂

      • I am reading both of your websites religiously at the moment. 🙂 I have been receiving treatment for ED and I thought I was doing healthy things by strictly doing all the paleo things I could. IFing, ‘perfect’ LC diet, lifting and sprinting….I was fatigued all the time, my poop was terrible, and my heart rate very low (40s) I was doing too much on a compromised body. I love that I learned to get over my fear of fat and stop chronic cardio on paleo, eating real foods, but doing everything bumped my estradiol levels down to 9, when it should be between the 20s-40s (or something). Now I’m getting over my fear of grains, eating rice and oatmeal, as I cannot shove one more sweet potato or piece of fruit into me. My energy is now fantastic, and so what, my ‘abs’ are gone, but at least my life isn’t about them anymore.

        The combination of these websites gives me support on letting go, while getting over the idea of looking a certain way and debunking some potential myths. Thank you thank you.
        I am just breathing through the healing…immediate bloating and fat accumulated to back and stomach, protecting those ovaries and kidneys….

        • Camila,
          “so what my abs are gone, but at least my life isn’t about them anymore.”
          Amen, woman.
          Thank you. Thank you so, so very much.

        • That was beautifully written, Camila. I too have had to let go of my abs -and slim thighs- in order to learn how to eat properly again. IFing and an extremely low carb paleo diet (Broccoli became a carb, I would only eat it post workout) led to binge/purging, insomnia and waking up half asleep to eat. I have gained 40 pounds since February and I still am not menstruating…it’s been over 3 years now. I still wake up at 2 am to eat whatever is in my pantry as if my body were still starving. Everyone is telling me how good and healthy I look but I have yet to accept it.

          • 40 pounds, hell yeah, woman. 🙂

            It will come in time. It takes a while to stop thinking “bigger” and to instead think “normal.” But once you see yourself as “normal” and as YOU, –just with some months and with some serious diversionary thinking tactics 🙂 – you’ll believe it too.

          • there is no doubt you are very much still healing and I’m supporting you all the way. Dipping too extreme does lead to binge/purging so when I get too restrictive, I have to ask myself ‘is this truly my preference, or am I denying myself something?’ I find that I still prefer paleo, after all the grains I let myself consume, but I won’t freak out and become ‘holier than thou’ over a sandwich. And remember, your body hasn’t balanced out until the hormones get in order, so just be patient until then. It’s so hard I know…I wonder who is thinking ‘well she let herself go’ and then I remind myself, it’s not about them. That takes a lot of strength and courage, so make sure you’re getting out and doing something that makes you feel SUPER good about you…display your best talent!

          • Wow, when I practice caloric restriction too closely, I found not only could I not get to sleep, but if I did, I would wake up and need to eat…nuts! The entirely wrong time of the day to eat if one is trying to lose weight!

            • So weird you mention nuts! That happened to me too! I’m doing a ketogenic diet (4 weeks in), and while I actually like it (I’ve needed to stop the carbs/sugars for a long time), I get the weirdest craving for – get this – Macadamia nuts(!) at like 3am! Wtf is THAT about?

    • Caroline,
      Hi! You have a blog about PCOS and nutrition? please share it with me! Are u at a healthy weight?
      After 3+ months of IF’ing I noticed it’s just not for me. Despite doing intense workouts my body refuses to lose weight. I don’t want to consume so much meat, but given that I have PCOS it seems like Paleo is the way to go…
      Thanks in advance!

  11. Great post. So important to emphasize that everyone is different. Two things worth noting. First, the differences between males and females on glucose/insulin/etc. make perfect sense in terms of evolution. Evolution is about reproduction. So if our ancestors retained an advantage in the mate selection game simply by indicating health and fertility via fat storage and weight management during times of scarcity, that would clearly be an evolutionary advantage. Second, sounds like women in the comments are already giving up on fasting, but we really can’t make any conclusions. It’s still likely that women can retain across-the-board benefits via bio-mechanisms like autophagy. For a healthy woman eating paleo, diabetes is not a risk, and fat loss shouldn’t be the principle goal — it’s just not important in the grand scheme, only in our culturally-brainwashed minds. I’m trying to avoid the trap of making conclusions as well, but these are all things worth thinking about. Sidenote to Pepper: every time I read your posts I’m inspired to write one myself. 🙂

    • Hah, Kevin, I remember still your “have ice cream with your guinness” post from more than a year ago now. Was one of my inspirations, back in my ultra-infancy. (Now I’m just regular infancy.)

      Re: evolution. Yes! So fascinating. What amazes me is that the woman’s body fights so hard to hold onto fat, and can get fatigued and sluggish, but once real starvation is detected, it almost throws itself in the other direction, inciting energy and increasing performance, becoming “masculinized” in order to find food. Food food food! It’s no wonder the modern woman has such a hard time bucking off the yoke of commercial foods.

      Something that worries me about all of this– I mean, the fasting– is that it can feel so great to be so alert and energized. Many women fast or live on super low carb diets for several months on this kind of high before things start going wrong. So while it is most important to listen to our bodies, definitely the most important, sometimes I guess this can also go awry.

      • Hi!

        One thing i’d like to mention: In the stone age, young women were most of the time either pregnant or nursing! In neither stage, fasting is a good idea.


    • Kevin, I think you put it very well. The fat loss shouldn’t be the principle goal indeed! I think it is more important to make sure that you just take care of weight management judiciously. Be circumspect, not extreme. That is absolutely the golden rule, and I learned this from my clinic professionals at montbelvieuclinic.com. Hah, Kevin, I remember still your “have ice cream with your guinness” post from more than a year ago now. Was one of my inspirations, back in my ultra-infancy. (Now I’m just regular infancy.)

  12. Thank you for this article. I have been doing 12-16 hour fasts daily since January, and one 24 hour fast/week since April, all while eating a paleo/primal diet and exercising regularly. I have seen zero results. I mean, zero. My body measurements are exactly the same as before I started. My sleep has never been good, and continues to be poor. My period, which has always been regular, became irregular in March. I am trying to get used to eating first thing in the morning again and stopping IF. I appreciate your article and wanted to let you know of my own personal experience with IF.

    • Thank you so much for sharing. And my sympathies for you in your trials, and excitement for you in moving forward gently and positively. As a side note, eating most of your protein when you get up and early in the day might help you not just with your meal timing but also with your sleep.

  13. I have been helping people with IF fasting including the “extreme” 72 hour fast. The is a huge difference in response between men and women. Men lose more weight and keep losing more weight after, women (especially those who went through the “change”) have a much harder time losing weight and usually have a much harder time losing more in the weeks following the fast.
    I did 2 72 hour fasts in the last year and a half, lost a couple of lbs in te first one and was totally hyper, I excersised 2 to 3 hours a day to get rid of the excess energy. The second one was a bit more relaxed, but I barely lost weight. The weightloss was not my prime motivator, but you do not expect it not to happen. I even had one client (a woman) that gained 1,5 lbs during the fast.
    There is a big reseach going on at one of the universities in the Netherlands which will track about 700 people. I will let you know what they discover about the male/femaile differences.

    • Thank you, Corine, that’s so helpful. I would love that information– I’ll go hunting for it online and see if I can track it, too. Anything you could provide would be great, even more on your anecdotal experiences with men and women. Do you have experiences with shorter fasts, too? That would also be helpful. What you’ve just shared teaches us that there are definitely sex-specific responses to fasting, but it doesn’t tell us necessarily where benefits and damages start and end (if they start and/or end at all).

  14. Thank you for the post, it was a good read. I think there are woman that take IF to far and go beyong listening to their body. I do however think it is a good tool to teach ourselves what real hunger is. I think far to often we fall into a routine with eating and consume food on the clock rather then when our bodies want it. I eat 3 meals a day and have never felt better.

    • I agree! It is so, so easy to let hunger fall under the bus in the modern world. It’s an important drive to be attuned to, especially for people coming out of disordered eating backgrounds like I do.

      All that said, I think restriction is a big part of why my appetite drive has been so messed up in the past. I understand it much better now– and I find that actually instead of overeating causing the appetite problem it was chronic restriction. If you ignore hunger signals long enough, whether through restriction or overeating, they change shape. This makes it difficult to understand what the proper amount to eat is. Anyway, it’s all very challenging, and the only real answer I can see is to be as nourishing as possible while testing different eating strategies.

  15. I tried IF last year, doing minimum 16 hour fasts. I’d read that it helped people to stop ‘obsessing’ about food, since they didn’t have to plan meals for a lot of the day & their time was freed up. I found it did the reverse. I found myself constantly thinking about food, when I could start eating the next day, when I had to stop, if I could eat dinner with my partner, when I had to eat before I went out. I have a history of disordered eating, which I still battle with, & this didn’t help. It really aligned itself with my tendency to be very restrictive. I would get angry with myself if I ‘slipped’ & had something to eat outside of the 8 hour window, even if it was because my stomach was growling with hunger.

    Most of the literature I had read, & the rave reviews, had been male focused or had come from men. After months of ups & downs, I gave up on it. I now eat when I need to, whatever time of the day it is.

    Thanks for this enlightening article.

    • Thanks, Natalie. I think you hit the nail on the head. The other half to bingeing is purging, and vomiting certainly is not the only way to purge. They almost never occur without each other. So if bingeing necessarily begets restriction, then restriction necessarily begets bingeing. Of course not always, but definitely among dieters, among people with body image issues, and among women at disproportionately high rates.

  16. Thanks! I put on a lot of weight after getting married and started fasting in the mornings. It has worked great for me and I was thinking of suggesting my wife do the same. After reading this I wont!

    She recently started to eat only breakfast and dinner because the food at work is bad, and her period is not regular anymore. Thank god she’s changing jobs, I suspect that if she starts eating at noon again (3 meals) her period will be regular again.

    • Oh, Omar, I am so glad. Best of luck. Know that healing takes time and patience and love above all things.

  17. Pingback: Jac's Countdown to 50! - Page 2 | Mark's Daily Apple Health and Fitness Forum page 2

  18. This post has come at the most perfect time ever! In the last couple of days I finally realised that my eating has gone way off track with sugar and caffeine cravings, and truly awful sleep patterns. I’ve been skipping breakfast and usually waiting until about 2pm to eat in an attempt to lose weight. I haven’t lost anything except my hard-won relief from IBS and anxiety. Thanks so much for putting this together! *heads for kitchen to cook eggs for breakfast*

    • Hooray! Jacs that’s inspiring. Glad to see you’re listening to yourself and taking care of yourself 🙂

  19. thank you so much doing all the the work you do, compiling research, grasping the science and adding your own experience. this has been a huge help for me to explain to myself, and the people in my life, why the ! i am so drained and the moment and why all of my energy needs to go into learning new habits and healing my system. you are so right on when you say the issue isnt even the over-eating, but the restriction. i have struggled with this for years, as the somewhere the cycle became binge in the afternoon after a morning of light eating and strenuous activity, then fast until i felt “detoxed” and “cleansed” and basically starving until i could eat again. the body does heal, and although it may take a year or so for my mensus to return, even after brining myself to the very brink of diabetes and pancreitis due to bad eating habits, this last month and a half of eating three square meals a day, no matter what, at the same time each day, even if i was only kinda hungry, and even if i didnt feel worthy of the meal because i hadnt busted my ass physically, i am able to eat a regular amount of food, put the seconds aside, be calm in between meals and have my mind on other things besides food and exercise. these small steps are amamzing for me and your posts are really helping to reinforce the better habits and intuitive eating. thank you!

    • Be re-inforced, Jessica! Gods, is your story ever familiar to me, or what. I would also fast all morning and afternoon sometimes, and then eat at night. Some nights I’d be “good” or what have you, and it would be fine, but other times I would way overeat, and then I’d feel fat/guilty/etc and would restrict again the morning, ad nauseum. I mean, it wasn’t always horrible, but I never really got any benefits, other than that I was able to hold onto my 18 percent washboard abs body with enormous willpower and at great detriment to my body.

      It is amazing and inspiring and so important that you are eating square meals whether you’d like to or not. Good, so good for you. Really. Own it, and share it, and unapologetically take care of yourself. With people like you leading by quiet example I think we might yet make something powerfully beautiful of womanhood.

  20. Thank you for looking into the detail on those studies. My body is reflecting similar results. While still overweight in April, I did 2 – 36 hour fasts and had great results. Now I am down to a high normal weight for my height and fasting has not done anything for my weight.

    • Once in a while, great, I think. That might work. As a life habit? Mmmmm disagree.

  21. Thanks so much for this article. When I am subcaloric, I experienced the same heightented activity and unsettledness as you, and sleep less as well. It’s a fine line- I can go somewhat under-calorie without this, but the intermittent fasting affects me like this for sure. I wish every nutrition scientist would read this and start realizing that there is 50% of the world, that like the ocean, is mostly uncharted territory as far as experiments and data go. Very frustrating, and we clearly need more women in science.

    • Working on it 🙂

  22. Thank you so much for this post! I think it is crucial to get more female voices in the ancestral health community– especially when it comes to fasting and carb restriction. After being diagnosed with PCOS last year, I began eating a “paleo” type diet and initially experienced excellent results. Thinking that things would only get better if I became more strict, I gradually reduced my carbs and started to IF– big mistake. Lost my period, gained weight, hormones went craaazy. Three weeks ago I finally threw in the towel and started a Ray Peat protocol (LOTS of dairy, carbs, fruit sugar, etc.) and finally ovulated after three months of amenorrhea. In the paleo community there seems to be some ignorance with regards to how delicate female hormones are… While fasting and going LC can be beneficial for some, the risks (in my opinion) greatly outweigh the benefits, particularly if you are a woman dealing with some hormonal issues.
    Anyways, thank you for your blog, I greatly appreciate you taking the time do this much needed research!

    • You too, Mari! Are you still doing the Ray Peat protocol? It has helped with your amenorrhea– has it helped with other health problems as well? How do you feel? What parts of the diet do you think are most helpful–are you maintaining caloric intake, eating to satiety, etc?

      As a side note on healing protocols, I have always had a bit of a sympathetic ear for Matt Stone. I feel strongly that we should never put toxins in our bodies, and that overeating is as much of a tax on a body as under-eating, but his radical voice is a powerful challenge to traditional norms. And also important. His overeating kind of diet is an intervention tool that can help certain situations, such as amenorrhea. Many women who have been amenorrheic improve eventually and slowly, but that is because they are being so careful to not gain weight. Others who, like you said, throw in the towel and go for menstruation 100 percent find significant and powerful hormonal results in mere weeks.

      Anyway, I’m totally fascinated by your experiences with Ray Peat, and I’d love to hear more about it.

      • I am a little hesitant to say anything too positive regarding my dietary changes because I learned the hard way that short term success can be very misleading. That said, aside from (hopefully!) restoring my fertility, the other health gains have been incredibly motivating: improved sleep, MUCH better digestion, more energy, clearer skin and a general feeling of well being. Two things I was quite surprised to find improved on a high carb/ high fructose diet: better blood sugar levels and less cravings in general. We’ll see how it all pans out– it has only been three weeks! I have to say though, having read a lot of Ray Peat’s work over the last couple of weeks, I am convinced he is very knowledgeable regarding thyroid function, female hormones and the importance of balancing estrogen/progesterone (all very important in understanding PCOS).

        You mentioned Matt Stone– initially I thought he was kind of off-the-wall, but I have gradually been coming around to his point of view… allowing the body to replenish glycogen stores fully and sending the signal that there is plenty of food can (I believe) be a very powerful tool for hormonal balance. I did the same thing (in a Ray Peat style way) for the first week after switching diets and certainly felt as though my body was breathing a huge sigh of relief. After my body felt replenished I sort of backed off, simply because I didn’t feel the need to eat past satiation anymore. If nothing else, the experience has certainly taught me a lot about biofeedback! The body is incredibly intelligent– we just have to learn to interpret the signals properly. My cravings and mood swings disappeared after adding more carbs and sugars into my diet– guess I just need some sweet stuff! Just my n=1 I suppose, but it has been eye opening.

        • Thank you so much, Mari. This is super helpful..and I love the way you’ve approached it. A perfect balance between self-experimentation and theory. I’ll add Ray Peat’s work to the middle-top of my to-do list. 🙂

    • I have done the Ray Peat protocol but after two weeks (and no period) I had to quit. My teeth were getting sore from all the fructose, and my heart began to race and I’d be wide awake between 12-4 am. I gained about 8 lbs more than I already had (I’d gone from an unhealthy 115 lbs to a much better 130) and then blew up more with the constant hunger that the fruit created (even paired with protein/dairy). Did the gelatin and OJ.

      I got really sick of the flavor of sweet things, and the dairy made me hungrier. 🙁 Maybe I didn’t stick with it long enough, but what told me to stop was the sleep cycle that got inhibited. I was sleeping so well before! Still no period at 137lbs and roughly 24% BF. I feel like I should have stuck with it, but didn’t know how. Especially with all my ‘hypo’ symptoms (orange palms, amenorrhea, coldness, dry skin, low pulse, vertigo). Of course all my thyroid tests/labs came back ‘normal’.
      The weight gain scared me off the most though. At this point it’s not necessary, but maybe my poor body is just so confused after dieting so long. :/

    • I too have tried Ray Peat. I found Paleo after a decade long search for a cure of Raynaud’s syndrome (cold fingers), eliminated wheat and grains and legumes, but didn’t have any luck with the Raynaud’s. After a couple of years with occasional IFing, and turning my brother on to Paleo (HE lost 60 pounds, I sure didn’t)…my health did a face plant.

      A stressful period in my life was accompanied by nerve tingling in a leg, and then anemia that had me napping constantly. I know it was anemia because when I tried to donate blood the tech said “see a doctor…” Single digit hemoglobin.

      Ray Peat was a godsend – the man explained that my basal temp of “normal” did not mean my thyroid was normal…96 degrees in the afternoon is NOT normal. Interesting to me how many Paleo (women) find Ray Peat after adhering to Paleo tenets, including IF, which exacerbates hormonal issues they didn’t know they had.

      I did the entire thing, the milk, the oj, the carrot, aspirin, salt & sugar, and progesterone, and my temperature shot up to 98 in the afternoons and the Raynaud’s was just gone, gone, gone. Granted, I gained 10 pounds, but the amount of things that I fear were going on that I was not seeing (e.g. – electrolytes tend to get urinated away when you are having thyroid issues, which is, I believe, why so many Paleo folks end up needing to supplement with magnesium for muscle cramping). And too, I have to add, I am glad to have potatoes back in my life! Ha… I’ll worry about the weight later.

      I am now on thyroid, and less strict with my Ray Peat eating, but following his advice proved to me that there wasn’t enough thyroid in my life. Since then, both my mother and brother have started thyroid. My father had been on it for 6 years without me knowing!!

      Ray is adamant that fasting is “stress,” period. And when you stress your body you can get into a vicious cycle with stress hormones that suppress your thyroid and throw you out of balance. While I was clearly genetically predisposed, and being female (I agree with your article! It’s not always for us…), and probably already having thyroid issues (the Raynaud’s for over a decade being a symptom), reducing carbs and skipping meals exacerbated my issues. Though, it can be said, hindsight is 20/20, and I wouldn’t have understood I had a thyroid issue until a crisis occurred!

      All that said, I have successfully lost weight and felt fine in my life when fasting when I was younger. But in my 50’s now, near menopause, it’s no longer right for me, just as it wouldn’t be advisable for a woman in pregnancy. Periods in our life where great hormone shifts are happening and we are at our most vulnerable to issues. Or so Ray Peat says! 😉

  23. I found this post to be very interesting. I’ve been IFing for about 2 months now (using roughly 14-16 hour fasting windows). My period, which is usually fairly regular, is three weeks late this month and I have definitely noticed mood and anxiety issues. I’m reluctant to give it up though, since it has seemed to help lower my weight set point and give me better appetite control (though I’m not sure if it’s entirely the IFing, since I modified my diet as well). I may try abandoning the fasting window idea and just using the modified diet while stopping eating by 6pm to see if I can get the same effect.

    • Yes! No need to throw it all out the window together. Change it reasonably and see if that helps, only doing what makes you comfortable. Your period will come back, it just needs a bit of love and tinkering. Though I would advise.. when in doubt, eat.

  24. I wonder if it’s a fertility thing. Like, if your body thinks, okay I’m not getting any food for a whole day, this is clearly no place to raise an embryo!

    I’ve just recently started doing the 8-hour window thing from that article last month (http://medicalxpress.com/news/2012-05-drug-free-intervention-obesity-diabetes.html) but that’s not really fasting, because eating from 11am-7pm is fairly wide.

    • No, that’s fasting. I think IF can be a good intervention, especially for people with insulin sensitivity problems, but you may want to be careful. The research I have done on IF shows that–at least for normal weight individuals–insulin sensitivity isn’t improved by women who fast. In any case, just move forward with caution and know if things start to go or feel off that you might want to considering the fasting itself.

  25. I love this blog – I got into paleo because of Mark’s Daily Apple and find it to be a fantastic resource but very male-driven. I read the forums every day and have noticed that there is so much disordered thinking about food and weight. People are latching on to any protocol that someone says worked miracles for them and bouncing from new idea to new idea – then wondering why their body doesn’t respond. Which then brings out the know-it-alls who are flat out dismissive of eating and exercise any other way but the way they prefer. I like this gentler, more rational approach and look forward to more female-oriented posts from you!

    • YES. I love Mark Sisson and I love MDA, but I have the same feelings and have observed the same, sad problem. I invite you to shout at them about this blog and this community as much as you’d like. And send people with disordered thoughts to me… I’d love to talk with them.

  26. Interesting article!
    Oddly, I regained my cycle after 3 years of hypothalamic amenorrhea while IF’ing – and I lost my period while eating 3 meals a day(breakfast lunch and dinner). I’ve recently started to incorporate breakfast again, but at a lower calorie amount and low and behold, my cycle is wonky again. For me, it seems meal timing is not as important as how much I’m eating.

    • YES. Calories are a very big deal. It’s hard to sort out the differences and the difference effects of calorie restriction versus intermittent fasting, and even harder when you start talking about all the different ways to fast. Level of metabolic derangement and disordered eating patterns, as well as neuromodulators and neurotransmitters, are also relevant. Lots of relevant things, I’m just trying to provide women with what information’s out there as they move forward.

      • And thank you for providing that info! I think this is the first article about IF that I’ve ever read that directly talks to the impacts of IF’ing on women.

        I sort of wish there were more studies on eating windows of 8-10hrs. It would be interesting to see if a daily fasting period of 14-16hrs has the same impact on the endocrine system as alternate day fasting does.

  27. Stefani when I read these rat studies I wonder what actually is the high fat/ high glucose diet : is it soy , vegetable oil and glucose diet which is the complete anti-thesis of the clean post fasting eating which IF advocates ?
    Also all the human studies are only on alternate day protocols.In your experience with fasting and clean eating would you say weekly fasting or bi-weekly fasting protocol may be more suited for women who face problems with sleep and cycles with alternate day fasting ?
    Do you think fasting is the cause of disordered eating or that post fast careless eating may negate the positive hormonal effects (which many other studies cite ) ?
    I am looking forward to your inputs .

    • Varsha,
      Yes, the HFG diets are designed to be “bad.” Note that they are not the controls, however. The control rats are eating the same standard lab chow (not ideal, but standard, at least) as the CR and IF tested rats.
      Yes, I would say that! I have no idea if it’s a good idea, just simply because there isn’t any research on it (really, there isn’t). Erring on the side of caution, I would only recommend fasting to women who have tried other methods and believe it may have medical benefits for them. Again, however, the few studies that are available– even if on alternate day fasts– show that women’s benefits are not nearly as pronounced as men’s, if present at all.
      What are the “many other studies” that talk about positive hormonal benefits? I’m just curious. If I missed something, I would please, please like to know. Many studies talk about cholesterol and cardiovascular health. I have not found many that specifically address female hormonal health (including insulin, etc).
      I don’t think anyone is doing post-fast “careless eating.” People who are undertaking IF are very serious about their health. If they are overeating after their fasts, it’s because something in their bodies is making them do it. Fasting I believe causes this appetite dysregulation, especially in women who have negative psychologies about food. Perhaps if women exhibited more positive body images and food relationships fasting would be less of a problem. Who knows.

  28. Thank you, thank you, THANK YOU! I needed this. I was wondering what was effing up my system and you have answered my question. I’ve been IFing for awhile and thought I was doing a good thing, but it stopped feeling good after about a week. This morning I am eating breakfast for the first time in several months and its going to be a good day!

    • Hooray! Breakfast ftw.

  29. I’m excited to start reading your blogs. You are adding a much needed addition to the paleosphere.

    For the past month I’ve been having just bulletproof coffee for breakfast (coffee with grassfed butter and MCT oil) and then not being hungry until ~2pm. I’m wondering what you think of this. It’s not fasting since I’m getting a bunch of calories in the morning, but the calories are almost all from fat. Dave (the Bulletproof Exec) talks about it being similar to fasting, because you stay in ketosis: http://www.bulletproofexec.com/bulletproof-fasting/

    Have you seen any studies of how women specifically respond to ketosis?


    • This is something I have wondered a lot about myself. Thinking about the biochemistry… I just don’t know. I think honestly at least speaking from my own experience that the fat eating is sort of like fasting, like you said. Most of the “I just ate!” hormones are signalled by carbohydrate and protein intake, at least in any significant amounts. When I just ate avocadoes all day until nighttime I experienced circadian dysregulation. But I am recovering from hypothalamic amenorrhea, so maybe women who are totally healthy have no problem with that.

      Erm, no. But I bet there are some. I’ll keep my eyes open 🙂

      • I followed Chris Kresser’s Personal Paleo for a month. I drank bulletproof coffee for breakfast because I was skipping eggs and dairy due to the autoimmune protocol. I just found it easier. Prior to that my breakfast was eggs with black tea and raw cream (which I had to give up). My period is regular but can be short. I average 25 days in my cycle. After 1 month I had a 28 day cycle that wasn’t super heavy as I would have expected. Other than that I really didn’t see any changes or improvements. I think the butter and MCT oil counts as food. I tracked everything I ate and averaged 2200-3000 calories a day at 75-80% fat. That’s just my experience, of course.

        This post was super helpful. It makes sense that women are more fertile when optimally fed.I was wondering how there could be a tribe of hungry, fertile men and fed, fertile women. It’s kind of interesting.

        I was also wondering what kind of job lab rat studies are with the daily rat pap smears.

      • “Most of the ‘I just ate!’ hormones are signalled by carbohydrate and protein intake.”

        I just found this blog yesterday, and last night I posted about what happens to my blood glucose (and, presumably, my cortisol) when I fast in the morning: it stays high. And I can’t sleep that night.

        But when I eat protein for breakfast, it goes down into a lower or normal range. And I sleep better!

        I repeated my experiment on another day with fat (in the form of decaf coffee + cream), and it did not lower my BG.

        I, as a Type 2 diabetic, wake up with high blood sugar. Getting it down asap is important to me! I’ve been IFing to lose weight; at least now I understand a bit better why it hasn’t been working, and why I’ve been awake all night!

  30. Great job, Stef. The men leading the paleo charge are all brilliant, but they’re MEN. When presented with questions about lady parts and lady functions, they’re totally stumped. Thanks for giving us girls the attention we need.

  31. I’m the author of a book on using paleo-related principles to enhance female fertility and pregnancy health, due in December from Wiley & Sons.

    I also don’t believe in caloric restriction, especially for women, because of hormonal problems and epigenetic signals it sends that reduce fertility. (ie “argh, a famine! Lack of food! Don’t reproduce, you could die!”)

    There is a simple way for women to realize the benefits of IF without the risks to their health. It’s called Bulletproof Fasting. Instead of going 18 hours without food, you have Bulletproof Coffee with a nice big hunk of butter and MCT oil in it for breakfast with no carbs or protein. Your body stays in ketosis and you get the benefits of IF because of it, but you also get to burn the fat for fuel. High levels of fat send the epigenetic signal that says “we are in a land of plenty. Make babies.”

    Does it work? Yes. One woman just lost 28 lbs in 28 days on Bulletproof Intermittent Fasting and told me about it this morning. For women, it seems to work better than IF, for the reasons outlined above.

    Oh, it works better for men too. Several have reported that they broke through weight loss plateaus using Bulletproof Intermittent Fasting that plain if couldn’t touch. On top of that, the cold hands, brain fog, and tiredness that come with IF don’t exist with Bulletproof IF. Our bodies were made to use fat for fuel – if there’s enough fat, we do well, and our hormones work.

    Adrenals matter too. IF, and Bulletproof IF, both rely on catecholamines to melt fat. If you are psychologically stressed or have adrenal stress, you need to fix that before you try any fasting protocol. Higher fat intake combined with more salt can do wonders for that. There is a reason that women crave fatty and salty foods – adrenal exhaustion. Eating them is a good idea.

    http://www.betterbabybook.com and http://www.bulletproofexec.com have more info on this technique.

    thanks again for bringing this to light!!!

    • Hi Dave.
      Thanks! I’d love to hear more about your book– is it the better baby book? That’s so exciting.
      I think you make an excellent point about fasting for weight loss plateaus. Fasting is often remarkable for women who are Overweight (With a capital O). Truly. For women who are normal weight, however, and looking to shed a few pounds here or there, then I think this is when fasting becomes a real physiological challenge for some women. I also think your form of fasting is a much healthier way to do it than just going without food at all. That being said, I’m still a bit wary of the completely fat meal for breakfast, because YES of course it gives people the insulin and leptin sensitizing effects of fasting–since it maintains the fasted state, but also the downside to that is that it is possibly this exact phenomenon–being kept in the fasting state–that is problematic for normal-weight/under-weight/stressed/some women. Honestly, I don’t know, and the limited research out there, to my knowledge, does not say anything definitive on the topic.
      Very much looking forward to Better Baby!

    • I have found Bulletproof IF to be very useful. The only problem is I’m sensitive to caffeine, so I prefer to go with decaf, but the MCT oil and butter do get me through the morning without stress. I’m not generally hungry in the mornings anymore, and I’m used to eating just two meals most days. I lost a little weight, started looking leaner, am very pleased.

      I’m post-menopausal so no longer concerned with fertility, but I still want to look good.

  32. First, yay, your site elevates the quality of dialogue in the blogosphere. Refreshing to find a nutrition site including critical examination of research, and feminist perspectives.

    Second, I didn’t read every comment, so I’m not positive whether this has already been mentioned. Just wanted to clarify that this statement from your article is incorrect: “nor have any studies analyzed reproductive responses to fasting.” There is a body of research literature studying babies that were in utero during Ramadan. In contrast with the erroneous claims I have seen on the internet that women have been fasting for religios reasons since time immemorial for zero negative effects, yeah they find some disturbing trends. I have not studied the lit in depth but it’s certainly worth exploring, regarding the question of fasting and reproduction.

    • You are right. There’s a huge body of literature on Ramadan and religious fasting groups. Those articles tend to be ignored much of hte time however because its so hard to parameterize people’s foods and behaviors during Ramadan. So many people eat different kinds of food on Ramadan as compared to their daily lives, as well as change their living and water drinking habits, etc.

      But you are right. That being said, it’s much less contentious, the idea that pregnant women shouldn’t fast. What I would like to see is studies on women’s reproductive health while they are not pregnant. IF you know of any studies like that– or ones that you think are worth the read about Ramadan and pregnancy (I’m leafing through them now)– I would be excited and grateful to hear what you have to say.

      • I agree that most of the info about IF is sex-biased, but I think the major problem here is that everyone is so interested in micromanaging every aspect of their lives. I am an IF opportunist. I never ‘intend’ to fast. But, considering the fact that this diet is very restrictive, especially in social settings, like our ancestors, when there is no adequate food around, I simply don’t eat, rather than compromising my diet. But, I never force myself to fast when I am hungry. If women truly want to listen to their bodies, then they will eat when they are hungry, and not eat when they are not hungry, or when there is no food around. It’s as simple as that. If they are following a healthy paleo diet, I don’t see how they can go wrong. As for Ramadan, I can’t believe that there is literature about pregnant women fasting. My exposure to Islamic practices is restricted to Morocco, which is a very liberal and modern country, and over there pregnant or menstruating women, the young and the old or the sick of either sex, DO NOT FAST. That being said, Islamic practices differ among different countries, as they each have a distinct culture. But, I just cannot believe that any pregnant woman would fast. That sounds like diseased fundamentalism, and not any sort of healthy cultural or religious practice. Furthermore, (sorry to keep going on and on), I worry a little about the trade-off in this article between mental alertness and fertility. Could this observance by the researchers be influenced by traditional misogynistic male ideas that men are logical and intelligent while the female breeder is illogical and emotional? Why contrast those two phenomena? Can women not be fertile as well as mentally alert? Why is it one or the other? And, what criteria are they using to judge mental alertness? I think we all agree here that women are just as intelligent (if not more so, he he!) than men, but no one can deny that our brains simply work differently, so you can’t expect women to take intelligence tests geared towards men and perform in the same way. That is simply perpetuating the old misogynistic bias.

      • I was on Atkins for one of my pregnancies. This child is now 38 years old. While my doctor would test me for ketones and then tell me to eat white food like potatoes, I ignored him. I didn’t have any problems except constipation, which I had with all my pregnancies. I did not want to be fat. I delivered and was thin for years after. A babe, for sure.

    • Old comment I know but it caught my eye. I’m a semi-observant Jewish woman with three kids born in 4.5 years. In Judaism, women who are pregnant or nursing a baby under 12 months of age are strictly forbidden to fast. We have 2 major fasts every year that require 26 hours with no food or water as well as shorter sun up to sun down fasts that allow liquids. As a result of the prohibition on fasting, it’s been five years since I last fasted for religious purposes. My female friends in the Muslim community say more or less the same thing: They are forbidden to fast, by religious law, while pregnant or nursing. I’ve found the same to be true in the Roman Catholic Church, which also observes fast days: Pregnant and nursing women specifically exempted from fasts.
      I myself become severely hypoglycemic while pregnant/nursing so it would be impossible anyway although paleo for the past few months has made my blood sugars stay far more stable.

      • I started fasting when my youngest of 4 was 4 months old. I am still nursing him and he is now 9 months old. Fasting has been wonderful for me with no ill effects.

    • I have to admit I’m kind of shocked by all of this. I grew up in an Islamic household and knew many other Muslimas growing up and fasting during Ramadan was expressly forbidden for women who were pregnant/nursing. I was always told that the Qur’an states that pregnant/nursing women were exempt because they were grouped in with the sick and traveling exemption that Muhammad, PBUH that says that you can make up the days later/give to the hungry and poor instead. Especially if Ramadan falls in the summer it’s a really bad idea to fast. That’s quite disconcerting. Just know that there are many of us that would never recommend a woman fast during those times.

  33. Fantastic post!! I find it so frustrating that there are tons of studies in the fitness and nutrition world that just don’t take into account the differences between the sexes!! Specifically, I’m constantly being told by other (male) trainers that I should try IF, because they’re getting such amazing results. I instinctually know that it will not bode well for me… if I skip breakfast, or even just go 4 hours between meals, I’m a mess. An emotional, panicky, nauseas, sweaty mess. So as much as THAT sounds, this post has given me the ammo to tell those guys why I’m never going to try IF 🙂

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  37. THANK YOU THANK YOU THANK YOU. I’m your newest biggest fan. I think that having a female perspective to look at the research and the data and the REAL WORLD results is critical, especially for those of us who are in that damnable state of “only 10lbs from superlean!” and thinking that we should aspire to get there no matter what.

    I do actually have a real comment:

    Here’s a general thought on the mice/rat studies that has been brought up in Calorie Restriction circles when they also talk about fasting (especially alternate day fasting): the shorter lifespan of the rodents completely screws up the data.

    Here’s why (theoretically, at least in the chatting about it): in a mice life, 1 day is like 20 days or more. So EOD eating is like eating for 20 days straight and then not eating for 20 days straight if you extrapolated up to us. For that reason, the negative effects they see COULD be limited to their little mouse bodies going “three weeks” without food, and not nearly as bad for us (anecdotal evidence notwithstanding, of course).

    It’s something I think about…. wondering if this has come up in your thoughts as well.

  38. I am so thankful for this post (and your blog as a whole)! The timing could not have been better. I am 26 years old, weigh 163 lbs, and I had been fasting for 3 months doing the “16 off 8 on” window. I loved it initially, experiencing high energy and calmness. On top of that I was keeping my carbs down (<50g a day) in efforts to break the weight loss plateau that I've been experiencing. All was well until a few weeks ago when I started experiencing severe fatigue, I missed my period (my period has always been very normal and never missed one before), and my face started to break out (never have experienced break outs even as a teen).

    After this I began doing some searching and found your site. Since then, I've stopped fasting and incorporated sweet potatoes, bananas, and berries into my diet (varied amounts) attempting to keep my carbs between 100 and 130g a day. The fatigue is gone (and time will tell on my period), but I have slowly begun to gain weight. While the health of my body is more important than the number on the scale, I would still like to reap a weight loss benefit from all this work!

    Where is the happy middle ground with carbs and fasting? I'm sure it's different for every woman, but do you have any suggestions as to where go I go from here?

    • Sorry, also when I was fasting I was keeping my daily calorie count between 1,000 and 1,200 calories. I have now uped that to 1,300 to 1,500.

      • Oh, yes! Good, Bonnie. That should help a lot, I think. I would also recommend you do as much intuitive eating as you can. At the end of meal, don’t say “can I let myself have more?” but instead “I can have more. Do I want more?” Restriction is a tough thing to recover from, but the absolute most important to put behind us, step by step, as we move forward into nourished health and womanhood. 🙂

    • Yes! I do. I believe the best thing is to do is to move slowly off of what you have been doing before. Increase your meal frequency, first, and add an amount of carbohydrate you feel comfortable with… and if you overshoot, just let yourself maintain or take a small step back and reassess…. 100 g/carb I think is good, a good base off of which to experiment. And fasting… I recommend a few meals a day. Haha. Sorry. Protein in the morning with BREAKFAST, carbs later in the day tends to do well both for people’s sleep as well as their weight status.
      I do believe health is more important than social norms, so I am glad that you are embracing your weight gain. That said, your weight gain is likely a simple starvation response. Your body had been starving, so it was trying it’s best to store food all along. When you begin eating isocalorically again, it hurries up to store it right away. Whether or not this ‘fat surge’ goes away varies by women, but I have heard many times that anorexic women rebound with a lot of weight, then once their bodies adjust to being fed relax again to a more moderate state. I have noticed a similar phenomenon i myself.
      However, I wouldn’t assert that you are experiencing any of this. Rather, these are just some things I have noticed that may be happening. The carb weight may also be water weight, or… well, we just don’t know. As you said, time will tell on your period. Really, time. And the breaking out… that is likely because of stress and disrupted hormone balance. Putting on weight should really help you with the acne. It increases estrogen levels, which can help mitigate the effects of high testosterone and DHEA, which may have skyrocketed in you as your body became stressed out. In all cases, I know weight gain (around 8 pounds? BF 18 percent to 20?) worked wonders for mine. 🙂

  39. This is fascinating. I started fasting back in February of this year, first twice a week and then up to 5 times/week, eating dinner only. Initially, it was great. I was fasting to lose weight and lose I did, maybe 7 pounds. I also TOTALLY got a ‘high’ from it. Come 3 pm, my finger tips would get cold and I would get this buzzy energy that I have never experienced on a more regular diet. Then, it stopped. I gained 4 pounds. I have been wondering what the heck was going on. I discovered that my thyroid is low (don’t know if this is attributable to fasting or not), and I also noticed that my last menstrual cycle was 35 days long! That is not ok, because it’s not my norm. Maybe it’s the fasting that has led to these changes? I have to say, I’m disappointed because I thought I had finally found a way to control my weight that made sense and was easy enough. But think about it, if you’re only eating one meal a day, that’s 1000 calories a day MAX, probably not even close to that in a normal dinner of mine, and to NOT lose weight on that? There’s got to be a reason. I have been thinking it’s the thyroid issue (I’ve just started taking thyroid supplements), but maybe fasting has been part of the problem. I wonder if possibly it might be a good tool for 3/4 times per year, and then cycle back into a regular eating regimen, maybe it mobilizes some fat if undertaken periodically, in the context of a 2-3 meal per day regular regimen (I have always hated breakfast so not sure I’ll ever quite get to 3 meals per day–unless you count opening the fridge and eating a cold chicken sausage with the door open a ‘meal’ 🙂
    Thanks for your insights.

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  42. I practice IF but was doing it before I knew what it was simply because I naturally avoid eating a lot of the time (even when I’m a little hungry). I haven’t had any problems and have even seen some positive results when combining IF with significant rest (for example: a week with no training whatsoever – endurance or strength).

    Also, hallelujah for a well informed Paleo blog for women!

  43. Thanks for the great reading! Wanted to share my experience as well…

    Don’t have my period since kinda 2 years now, did some bloodwork and it was like kinda all my hormones are low, FSH, Progesterone etc, even Testosterone and S-DEHA were low (Testo near the bottom borderline, S-DHEA even below).

    Thing is, this was like that even before I even got to know that IF exist. Back then I was eating 6 meals/day with actually no calorie restriction. I must say I was not that lean back then, I would say 18 bis 20% BF but well…

    Now I have being IFing (16/8) since September last year. In the beginning, the resuts were absolutely great, lost fat, kept muscle… Now, nothing really happens/changes… I was doing kinda cycles, high carb/low fat on training days, high fat/low carb on off days.

    Went in March to my FA and he gave me pills which are actually prescribed to post-menopause women as hormone replacement – to see if I get my period back. I’ve been taking them for almost 3 months now and still no period. And I did change my diet to make sure I am not on CR, and I DID gain 4 pound since I started with the pill and changed my diet, but still nothing.

    So I am thinking about reducing the fast-window to ca. 14 hours, but as I said, I lost my period long before IF so I don’t really think this is the main reason. Besides that, As I am already gaining weight, CR shouldnt be an issue in this case.

    Any thoughts on this?

    Thanks a lot!

    • Sounds like you know what I am going to say. 🙂 IF less, gain weight, decrease stress. Nothing will pull your hormone levels up like convincing your body you are fed. Time, too.

      • hey, thanks for the quick feedback!
        The thing is:

        1. I had this issue even before IF/without CR and back then I was weighting 6 pounds more than now… So I am not sure if this will be enough, you know?

        2. I have been gaining weight and taking these pills since almost 3 months now and still noting from my periods, so I kinda got worried now. I thought 1 month taking the pills would help already, you know?

        I have “bad genes” concerning cancer on my family (ovaries/breast cancer) so the last thing I actually want is such hormone replacement stuff 🙁

        Thanks a lot!

  44. Hi i am a 25 yr old female with a BMI of 40 MY BMI was 45 but i have change that without IF but it was very very difficult i have recently started IF for about three weeks now and i never would had searched IF for women if it had not been for menstrual. On day one i experienced shaking, i began to prespire significantly while doing almost nothing and then i thought i was going to pass out and realized that my sugar might be low so i found some honey grham crackers and and apple and in 30mins i was ready to go on with my day feeling extremely better. However im concluding that i cant really IF on my menstrual days and if do it needs to be 16/8 and not 19/5 or 18/6 like i normally do. I love IF im down two inches on my waist in two weeks and i feel great most of the time, except when it gets close to my fed time im ready to eat and start to get anxious ive realiezed that i am more awake/alert at night and in the morning versus the afternoon which is weird and i want to change that. however, my menstrual was lighter than normal on the first and second day which are usually my heaviest days, but i have concluded from theses studies (the human one) that since a womans fertility decreases even on a 20 percent CR then she is more than likely to decrease fertility rates on any diet. which makes since to me because how can the body worry about making babies when their is a shortage in food, how can a woman carry a baby under these changes? what i want to know is once the “famine” is gone and in my case the majority of my excess weight, will a womans fertility return to normal? i dont mind not being able to conceive diuring IF because IF Isnt for pregnant women anyway. so these studies dont really answer the real question or the real concern. Please let me know what you gals think

    also im down to participate in a study on IF. if anyone knows about one let me know. thanks

  45. Interesting reading like always. However, I’m not totally convinced IF is an issue in itself, as far as fertility goes. My guess is that IF is often CR in disguise, and CR is the real issue. I’ve been on a 1 1/2 meal per day for years: one light breakfast in the morning, then 1 big (BIG) dinner in the early evening (which typically lasts for 2 hours with my partner and baby). Then nothing till next morning. This feeding schedule has been working great on me. I would not recommend it to others though; I guess everybody is different. But for me at least, I’ve noticed that as long as I eat enough calories and high quality food (lots of healthy fats in particular), I’m fine. I fell pregnant immediately when my partner and I decided we wanted to have a baby. Maybe we were just lucky, who knows. All what I’m saying is that I may not be the only one for whom IF works ok, and maybe more research is needed to fully understand the impact of fasting on fertility in humans.

  46. Wow, I totally read this article while thinking, oh well IF has been great for me. It cured my constantly thinking about meals when I ate five to six a day; It made me realize what hunger felt like; It stabilized my energy levels and eliminated my mindless snacking and any emotional eating. So yes some great benefits.
    However when I thought back, I started to realize about three months into IF ( I lost no weight, and truthfully had none to really lose) experienced a total 180, where I went from high energy levels to total extreme and utter fatigue. I complained about ths because the great contrast baffled me. I began taking b vitamins ( my sister is a nurse, and told me our bodies store this so it is unnecessary but I still do it) and also iron on occasion ( despite knowing I get more than enough protein). At this time when I got blood drawn in the morning before I broke my fast, I was told that my blood was unusually viscous, came out very slllllllow, my hr was in the 50’s ( which worried the MD but we decided it is because I was moderately to highly active)., and my BP was about a 100/80. I actually took all this as evidence of good health except the unusual fatigue.

    I admit that I am still fasting but at 20% measured body fat, my continued focus on fat loss may be more vanity than any increase in health and as a physical therapist I should know better:-(. So I definitely have to rethink the caloric restriction combined with fasting and in retrospect think that is where the real issue may lay. I think fasting makes excess caloric restriction very easy and with the pro- Ana and orthorexia prevalent among low body fat women, striving for fat loss may wreck irrevocable damage.

    Thanks so much, because I read so many fitness blogs, I find way more support for my IF and caloric restriction than naysayers and it is easy to be dismissive. I’m fit, get my veggies in yet always feel like someone out there is more dedicated than me, because they practice more restriction. Disordered thinking? Yes. Frightenly common? I think so. BTW I am 24, so fairly young, and would hate to wreck irrevocable damage but I do love fasting.

    • The high blood viscosity issue when you had your blood draw was probably due to dehydration. Drink plenty of water!!

  47. No offense to the people that have had issues with IF but seems to me their issues are possibly related to a lack of calorie deficit. In my personal experience fasting is a great way to lower calorie intake. For me, it is easier to not eat at all than it is to eat the tiny meals I would have to eat to lose weight on 3 meals a day. Is it healthy? Maybe, maybe not. But it sure as hell produces weight loss when you only consume 500 calories a day. If you fast and then pig out to get your “allowed calories” you have just undone the restriction you created with the fast. It is simple math, eat less and your body will have to burn fat. The same way that eating too much will cause you to gain fat. Of course there are many other factors, but almost all diet failure is from the lack of a sufficient food deficit.

    • Actually the opposite is true, most of the problems people are talking about are also fairly consistent with anorexia. Hair falling out, fatigue, menstrual dysfunction, achiness, all suggests insufficient nutrient intake coupled with an excess calorie deficit. Eating only 500 calories a day is kind of insane and may wreck irrevocable metabolic

      Health should always come before weight loss. IF when used with stupidity is really just starving yourself. IF when used with common sense can help create a mild caloric deficit which combined with exercise can provide successful and MAINTAINABLE weight loss without the deprivation usually reported with strict diets. Women with pro ANA or other emotional, psychological leanings towards disordered eating are no 1 prime candidates to warn away from IF.

      500 calories a day = LONG TERM dysfunction.

      • I am not suggesting this large a caloric deficit is necessary every day, but when done occasionally it helps weight loss. I just notice from a lot of comments that people post on IF discussions that people seem to overcompensate after fasting. What I am trying to say, is that there is nothing magic about eating all your calories in a certain time window. The magic is only in the deficit. If you fast but fail to create a deficit, you will have no luck with weight loss.

  48. Thanks so much for this article !
    I have experimented with alternate day fasting (eating only every other day, thus resulting in 32-36h fasts) in the past and had, though not overweight – 150 lbs/5’4”, great results: i was able to shed 10 pounds that I wanted to lose and really enjoyed the increased satiation after a meal on eat days, feeling on the whole much less polluted by my slight, but constant overeating …
    The only thing that really bothered me on fast days was the alertness at night, resulting in difficulty to get to sleep. The fast days were no problem, but the moment I went to bed I often would lay awake for two hours before I was able to go to sleep. I felt giddy, energized, and restless and would often wake early in the morning high alert and feeling slightly sick … every testimonial I turned to would tell me that these were mere “growing pains” of my body’s adaptation to IF, but those symptoms didn’t improve and made me doubt the health benefit of it.
    After a break from IF I readapted my IF regime recently, only doing 2 fast days per week, but your article made me wonder wheter I should decrease the length of my fasts. Not eating the whole day works far better for me than the “eating window method”, but I wonder whether a small snack (high in carb ? or fat ?) right before going to bed (so 24 to 26 hours into the fast) would help with the difficulty to doze off. When eating normal I never have any sleeping issues, although I tend to overeat at night. Thanks so much for your insight !

    • I think the nighttime snack could do wonders for you. I wouldn’t guarantee that it’ll make you sleep– personally, if I fast a lot during the day, sometimes a big meal won’t help all that much at night, but it’s totally worth a whirl. High carb I think would be better for sleep, but you may get by with fat as well.

    • I do the fast diet too. One day i will fast and eat under 500 calories and the next day eat what i want.I don’t think i would keep up with it if i could not eat at all on the fast day.I think you will be ok to eat a little something before you go to bed on your fast day…and by the way this is the best most effective diet i have ever tried.it is something i will continue to do always even when i lose all the weight.

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  50. Nice article! I started doing mini-fasts since about 4 months ago since I decided to give IFing a try. I only say mini-fasts because i just don’t eat breakfast (but I do have some coffee with some cream in it). Ever since starting to do that, I find it easier to control my hunger and not to over eat as much (I’ve always been more of a night eater anyways). My energy has not decreased and I actually find it easier to focus on my studying for tests and everything since then. The only thing is why I was wondering why I still wasn’t really losing weight since I can control my hunger better. I guess this explains that. It’s not that I’m over weight or have a lot I need to lose, but I have gained some since starting college, and it’s so frustrating that I can’t get rid of eat even though I am eating primal.

  51. Wow — I have tried IF numerous times. It is wonderful for me for weight loss, but I absoultely cannot sleep. I feel hyper, can lift significantly more weight, feel alert, energetic, etc. But no sleep. And it lasts for days after I eat normally again. After 2 or 3 days of not sleeping, I really start to drag and have trouble focusing… but I still feel buzzed with energy. It is a strange feeling.

    I would love to better understand why this happens. I find I have the same response (though not quite as severe) when I eat VLC…. totally cannot sleep. At best, I doze in and out a bit and end up getting up at 3:00 a.m. to start my day.

    • I may write with more of a focus on this at a later point in time, but I did touch on it briefly in this post. Hippocampal upregulation and hypocretin neurons both detect starvation and upregulate arousal. The hippocampus also causes females to have increased alertness and memory function. This is presumably an evolutionary adaptation against starvation. Unfortunately some people get hooked on it, and this plays a role for some women’s anorexic tendencies.

  52. Thank you so much for this article. I have never done well on eating plans that promote IF or severely restricted calories. Last year, I severely restricted my calories and IF’d for 6 weeks, only to gain 4 pounds. And believe me, it wasn’t muscle! :\ Also, I notice that if I fast – intentionally or not – I get hungry less and less often. It seems like in the years that I tried to fast and/or severely restrict my calories, I was never hungry, no matter how much I exercised or how active I was (including 100 mile bike rides!). It was only when I started eating regularly (especially breakfast) that I started to feel hunger again – it even took me awhile to realize what I was feeling! I am now slowly losing weight, but I am very careful to eat when I’m hungry and not fast. It doesn’t work for me right now.

  53. Hi, thanks for writing this article.
    In April of last year I had 8 teeth extracted and did not feel much like eating after the surgery so I unintentionally lost some weight. (I probably weighed around 128lbs at the time: height 5’4 or 5’5; Body fat probably in the low 20s, now 20 years old) Anyways, I looked in the mirror and really liked how I looked then and because of that continued the calorie restriction with no real idea of what I was getting into. After that I had one more normal period before they disappeared for a year and two months. Once I realized what was happening I tried to eat more and stop worrying about the nutritional stats of everything I was putting in my mouth but would get nervous and go back to more restriction when I gained (or at least looked like I gained some) weight. I went to Japan that fall and ate like crazy, thinking that would be enough to bring back my period) but that did not happen. Once I got back, I learned of the primal/paleo diet and changed my diet. During the first few weeks of eating primally I ate like crazy and felt great but then I got anxious again when I appeared in the mirror to be gaining weight. Thus started my journey with IFing. I found IFing easy. In fact I skipped breakfast and lunch all the time as a young teen. However for me, IFing eventually caused me to be thinking about food all time and I was getting quite obsessive about it. Also, looking back, I had other symptoms of not getting enough food (even though I should have been eating enough calories I eat like 2300 cals a day) and I somewhat knew it but could not muster the courage to let go and eat more. Those symptoms included fatigue and taking a ridiculous amount of time to recover from sore muscles, my hair got thinner and the color changed a bit and I probably had heightened anxiety as well. I noticed things got better when I ate a lot but I was never brave enough to keep eating more cuz I saw a probably small weight gain and then freaked out. About a month ago I spent several days being so so tired for no reason, sleeping more, getting dizzy upon standing from low blood pressure and had muscles that felt like jelly all the freaking time (even going up and down stairs were too much). That was enough for me to take the leap into eating more and I decided that I would stop worrying about whether I was hungry or not and whether I should eat now or not by definitely eating at noon and at 9pm or so whether or not my stomach was growling and to eat until I was definitely full. I got markedly better day by day and felt good again and starting having more energy for things. I probably have gained weight but am trying not to focus on that for I am sure I will lean out over time though the one thing I noticed was that when I ate more and felt better, I was way less likely to look at myself in the mirror and see a “fat” person. Instead I started seeing a more normal body shape and was more pleased with that body shape and that helped me let go more. I only intentionally IFed twice this month and that was just for the one thing I found IF useful for-gymnastics meets. Anyways, I finally got my period back three days ago out of nowhere. The more regularly I eat, the less I feel the need to eat a ridiculous amount at one meal (by which I mean spending 2 hours doing nothing but eating or waiting for food to finish cooking), the less I feel like I am obligated to eat everything on the plate and the less I worry about food in general. Reading this article makes me want to try adding breakfast back in my daily life and see what happens. Thanks.

    • Thank YOU for sharing, Rebecca. This is exactly the journey I am talking about, and I am so happy to have your experiences aired… it ALL is so familiar to me. The constant back and forth between restriction and not… the “hitting bottom”.. the conscious decision to let go and let intuitive eating take control… that’s inspiring. And especially to hear you got your period back. 🙂 Congratulations! That really is so inspiring. Thank you again.

  54. Comment

  55. I’ve been doing a simple form of IF for about 2 months now, where basically I just don’t eat breakfast. I eat my first meal around noon. But my understanding of IF was that it’s basically a way to encourage your body to access fat stores, and that restricting calories further during IF is not appropriate. So every day starting around noon, I eat like a longshoreman in order to get in all my calories. Since I have some days where I get up and do P90X and then shower and head off to yoga class before returning home to eat, that can be upwards of 2000 calories. So I eat like it’s going out of style. That’s actually what I have been loving about IF: this funny situation where I have to eat like a frat boy trying to win a bar bet. It’s hilarious.

    Perhaps because I have worked so hard to maintain a good caloric intake with plenty of fat, I have not experienced any bad side effects. My sleep is excellent and my menses are regular. (I am 42, so you bet I am keeping an eye on that situation.) I have lost only about 4 lbs in this 2 month period. I have certainly experienced a feeling of tremendous energy and well-being.

    Anyway, I’ll be finished with P90X in mid-August and I believe I’ll take a break from IF then. I don’t feel it would be good to do it indefinitely.

  56. I started IFing(by accident really) back in December by skipping breakfast and only eating a late snack and then supper. This was because eating in the morning was causing some weird issues with dizziness and fatigue soon after I ate; plus it was so busy at work, I was lucky to get any time to eat anything! I lost 5lbs, skin was great, felt good yadda yadda…then one month my period was a week later(I’m like clockwork, if I’m late, I’m pregnant) Considering the fact my husband got snipped the year before, I was freaking out. I ended up gaining 10lbs in 2 weeks and another 5lbs since. I also started breaking out like crazy including on my back which has NEVER happened before. My temps are between 96.5-97.5 f where they were 98.9f consistently. Add on extreme fatigue and insomnia (I actually have to nap now! I need napped before in my life! Ask my mother, she can confirm 😉 My adrenal fatigue came back full force, and I’m pretty sure I’m not estrogen dominant.
    I feel like an idiot now, because I’m just starting to realize that maybe it was the fasting that did it. I’m eating more regularly now, but I’m not sure what to do to get rid of the extra weight.
    It sucks though, there is so many great benefits to fasting. I guess my body just isn’t one to handle it like some women can. I wish I had known about this before I let myself fall into IF.

    • Wow! I thought I spellchecked that first! Add in brain fog…
      -“I need napped” I never napped
      -“I’m pretty sure I’m not estrogen” I’m pretty sure I’m now estrogen

  57. Well done. That was so needed. Women are very different. If you read sites like radiantrecovery where women are trying to moderate sugar urges with 3 meals a day, no snacks which helps over eating, depression, levels of seratonin in the brain the idea of having a fast would be anathema.

    I suspect for 1 million years our female ancestors were rooting for berries and roots and insects all day and probably eating several meals whilst men may have been out on long hunting trips often coming back with nothing and having fasted.

    • Exactly! I know I’m a couple of years late here, but to anyone reading these comments, this is what makes so much sense: we were hunter/GATHERERS. Women were gathering and snacking all day. Men often weren’t. If we’re really thinking paleo, we need to consider this.

  58. thank you for this article! it was very illuminating. I have done IF a few times now. It is very easy for me, im never hungry, it gives me a ‘high’ and i get extra alert and productive, i can do my crossfit WODs no problem and then not eat anything for hours. however i did notice my period is all over the place, i get stomach upset and on the non-IF days i’m so down and craving sugar! it is good to know that i don’t have to fast anymore, whew. Brilliant info, i’ll be sharing this one around alot 🙂

  59. Thanks very much for this great article and for all the views of other women who, like me try to listen to their bodies. It feels much better knowing I’m not alone in this mine field of how best to take your nutrition on board whilst acheiving what you want to achieve!! I will continur to listen to my body:)

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  62. Even within women (and men) there are many individual variations. I have eaten multiple different diets and fasted in different ways and think that there are healthy ways to fast – but not for everyone and not under all circumstances. When I fast I ALWAYS do enemas or implants of some sort – and there’s a big difference in my body’s response if I don’t get around to doing these. Ayurvedic information has also been critical in my initial understanding of what makes sense. But in the end my experience has been that with a relaxed observational attitude and a well developed intuition that we often know what makes sense and the scientific studies just confirm what we knew. Unfortunate that most of us live overly stressful lives and can’t notice physical details.

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  64. I love this blog on IF. My mom and I are both learning about IF and it’s great to see this post directed specifically at issues for women. I really enjoy reading the comments section so we can hear from women with different experiences. It keeps it all real to have the open admission that we can be different and still be part of a community that celebrates healthy choices.

    • Hi – I wanted to add to this discussion of the research around IF for women. I’ve tried it myself and with variable results. I just wanted to add a link to a more recent study – specifically on women comparing IF with calorie restriction which showed no adverse effects.

      It was published in the International Journal of Obesity in May 2011 – entitled

      “The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomised trial in young overweight women”

      xx Ellie

      • Hey, thank you, Ellie. I definitely need to look into this. (I think there is probably a significant difference between normal and overweight women) I’ll start digging 🙂

  65. I was guided to your website just today, and I am overjoyed!!! So many topics that interest & concern me, and you seem like such a compassionate & knowledgeable person!!! 🙂

    (I just wanted to share one thing, but it turned into more. Hope y’all don’t mind the long post!)

    I am 40 years old, would like to lose at least 100(maybe 120) lbs, was diagnosed with diabetes 15 months ago, and have been doing IF/JUDDD (or attempting to do so) since October of last year (did low-carb for about a year before that). While I had some great weight loss at times (6lbs one exciting week!) and really enjoyed the benefits of lower grocery bills & fewer dirty dishes (lol), it’s been frustrating overall (20-25lbs in the same time that others in my online support group have lost 50-70lbs) and I have struggled terribly with insomnia.

    One night, as I whimpered & thrashed in bed at 3 or 4am, exhausted and BORED, I realized that I had been trying to fall asleep for about as many hours as I had pushed back my 1st meal of the day. Hmmmm…

    I did Jack Kruse’s “Leptin Reset” for a while, and the very first time that I ate an early, high-protein, no-carb breakfast, I fell asleep quickly and at a reasonable hour that night. A few days later, I had (not low-carb) pancakes for breakfast, and was again sleepless that very night; it didn’t take a few days for the benefits to “wear off”. So it’s not just breakfast I needed to eat, but protein.

    Slowly I worked my way back to doing JUDDD and/or Fast 5, because I love it in many ways, but weight loss wasn’t happening and insomnia was coming back.

    This week I started looking into the cortisol-fasting connection (again! I have been hearing/reading about it for many years) and decided to do a little test a couple days ago.

    I took my fasting blood glucose when I woke up at 7:22am: 132 (average for me).
    I went grocery shopping, came home, did housework, ingested nothing but water. 11:34am: 125 (not good!).
    I had a non-fat protein drink (gelatin + a little whey, approx 100 calories): 103 an hour later! 102 2 hours later! Awesome!!! (For me! Plus my meter reads a little high, so that might have been more like 85-90.)

    Also, I fell asleep earlier & more easily, although I did begin taking melatonin that same day. I hope to use it only temporarily, while I “reset” my sleep schedule.

    If I understand/recall Dr. Kruse’s and various other explanations correctly, cortisol is high in the morning (and causes blood glucose to rise–the diabetic’s “dawn phenomenon”) but can sort of get “shut off” by eating protein. The fact that my BG remained high after several hours of fasting and mild exertion suggests to me that my cortisol remained elevated as well. So…sort of a waste of 4 hours, health- and weight loss-wise!

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  68. Thanks for this article! I’ve tried IF, and while it gave me great morning energy, I gained weight on it, and could not maintain regular fasting. (I was trying to crunch all my eating into a smaller window–5 hrs, then 8 hrs when that didn’t work, then 10 hrs.) Ultimately, I gave it up, as it was very difficult and obsessive, and didn’t work for me. Pushing back the first meal of the day caused me to want to obsessively eat at night.

    But, I keep reading all these articles about how great IF is for you, so I keep thinking I should try it again. After reading this, I’m going to listen to my body and give it up. Fasting may work great for most men and some women, but not for me.

  69. Well, isn’t this confusing? I had been trying to conceive for 6 months, then started doing two 24 hour fasts a week. I lost weight and did not suffer any of the side effects you mentioned. In fact, I got pregnant right away! I even had PCOS! I don’t see how thats possible if all that research is correct. Oh, well! I plan on resuming IF after I have this baby.

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  72. Interesting post. I just listened to your podcast on the Abel James show, which linked to this article.

    I’ve only been on a paleo template since April. Prior to beginning, I was not unhealthy. Forty, moderately overweight but fit because I’m an athlete, but I had no hormonal issues or other health problems. IF has occurred somewhat naturally for me in this process as I am just sometimes not hungry in the evenings, or at lunch, and thus skip a meal. This occurs several times a week. I’ve also noticed that if I’m not really hungry in the evening, that skipping dinner (which usually only occurs when I’ve had a decent-sized lunch) means even better sleep, which I believe is tied into the circadian rhythm issue. I, too, am very interested in pulling out the sex-based differences for men and women regarding paleo diet and IF. There are so many factors to consider and this is yet another example of there not being a one-size-fits-all approach for any of these ancestral ideas. Thank you for taking the time to cull through this research and to provide a very thoughtful post. I just joined your community and look forward to being a more active part of it!

    • This is where we differ. I am never ever not hungry 4 hours after a meal even if it was all fat or loads of protein as most of mine are. I suppose that is why I can never do IF and if meal is 2 hours late then I am needing to eat massive quanitites of fruit, meat even, nuts as my body thinks it is very unhappy and being deprived. I wish I could get like you – that you just aren’t hungry. Mind you I often eat when not hungry any time from after lunch on on almost every day. Taht is my main issue – sugar addiction (which will be nuts and fruit when I am sugar free).

  73. Thanks, some great food for thought. As we’re currently trying to conceive I thought I should knock IF on the head. I’ve just googled for calorie restriction and fertility (as I’d still just like to get a handle on my overeating), and there’s all sorts of articles coming up about calorie restriction increasing fertility in later life!!!! Talk about not knowing which way’s up!!!

  74. Hi,
    Thanks for this – interesting! I wanted to share my experience. I’ve been following daily IF for more than 3 months and am not having any adverse effects. I’m of normal weight and do a 16 hour fast with an 8 hour window. It’s very easy and I don’t suffer – very little hunger – usually when it’s time to eat. It has also greatly reduced my anxiety about food and when to eat. I also follow the Perfect Health Diet (paleo/primal with safe starches and dairy) http://www.perfecthealthdiet.com. Sometimes I have a TBS of coconut oil during the fast, sometimes I don’t. When I first started fasting, if I didn’t have the coconut oil, I felt terrible and light-headed. Now I can go without it with no problem. I do intervals on the recumbent bike several times a week during my fast and am fine. I also sleep fine and have regular periods. Maybe I’m not having any problems because I do follow the Perfect Health Diet and make sure that I’m not getting too much Omega 6 (very little chicken/pork which are higher in omega 6) and plenty of Omega 3 as well as not going too low carb and getting safe starches such as sweet potatoes, white potatoes or rice as well as some fruit. And another thing I do, per Ray Peat, is that I eat some raw carrots on an empty stomach. (This has an anti-estrogen effect.) http://raypeat.com/articles/articles/natural-estrogens.shtml I eat them about an hour before my meal. Anyway, just wanted to share my experience with IF. Thanks!

    • Wow, thanks for the raw carrot tip– I have been grabbing a natural (not “baby” processed) recently as a quick snack when the afternoon hungries hit, and (probably not a coincidence after all!) my hot flashes have abated after nearly 15 years. I had no idea carrots were antiestrogenic.

  75. Hi!
    I was reading the article but all the information really boggled my head so I just wanted to leave a question …
    I’m 16,5’3,120 pounds and 19%BF.
    Would the 16hr fast be better every day or 24hr once a week?

    • Neither. Why would you want to fast? Perhaps you want to first consider your motivations. Looks like you’re thin enough, if not too thin, so why fast? There’s no reason to do it so far as I can tell.

      • I want to drop body fat percentage to 17% and lose some stubborn belly chub, what would you suggest for that?

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  78. I had a notion, so I’ll just throw it out: If the reason people (me included) do paleo and the reason people do fasting is to get “back” to the more primal way of doing things – then why does it matter if the female body reacts differently than the male body? What I mean to suggest – if fasting is good for the guys and they point to evolutionary history as proof for doing it; shouldn’t girls point at the same evidence and say “adrenal failure be damned, I’m IFing” – that’s how we got to be here. Maybe this was natures way of birth control and only the able have the babies. Paleo women had to endure “adrenal failure” all the time by the looks of it; unless we suppose that food shortages only affected the men. Any way, great article!

    • Oh…

  79. Not sure if anyone will see my little comment all the way down here, but… 😛

    I’m really glad I came across this post. I don’t have PCOS, though I have longtime hypothyroidism (had a complete thyroidectomy a decade ago) and ovarian cysts that are being treated through birth control. I had been great until I delved into the world of IF, AF, and JUDDD. The last two months (even though I had been regular like a dime; I’m 23, btw), I’ve had “surprise!” spotting days before my offweek. I’m not pregnant, but now I’m wondering if my IF has played a role.

    Any thoughts?

  80. This is so interesting, thank you for posting and for everyone’s comments. I have been reading a lot about IF and all the other hyped losing weight methods over the past 6 months. I IF at the weekends and sometimes during the week without realizing due to being busy etc but it is usually only in the mornings. However I was following a different healthy eating plan for the last 6 months and have found the following results-during an incredibly stressful period (work related) I had my period for 3 weeks! I am usually someone who you can set your clock to. It was awful as it has never happened to me. I have put on weight and now back to my negative though pattern about myself which are on the verge of starting my anorexia again. As I am aware of all of this, I am putting myself back on my usual healthy eating plan with no IF or weird tricks. I think it is so important that the affect on the ovarian and menstrual side of the female body is looked at in real scientific detail before females continue with IF way of life. I am pleased I’ve realized this before going further as my husband and I want to start a family. I am already “old” in the reproductive world- 35, so need to be as good to myself and my body as possible. Thanks again for this post

  81. I found you via your interview with Abel James the day after my 4th and last experimentation with IF. I was trying to do it once a week. I am pretty much at goal weight, but the health benefits I read about IF sounded very good. I have been reading Bulletproofexec, and even read the post about fasting and women, which features you.

    I am post-menopausal, in nutritional ketosis (I eat low-carb high fat) and can go (finally!) up to 5 hours without eating. I’ve been eating low carb for 1.5 years. I am not restricting calories at all and do not have a history of problem eating. All this to say that I thought I was in good shape to try it. I tried the bulletproof fasting (16 hours: only coffee and plenty of grass-fed butter & MCT oil in the am) which is supposed to be better for women. What a nightmare. The low blood sugar feeling and bad attitude was back and, basically, the whole day was ruined. I did not experience any improved mental sharpness or any other benefit. I had been sleeping much better since eating low-carb, but either the day of the fast or the next day I couldn’t sleep.

    Even before listening to your interview, I thought, it’s not worth ruining 1/7 of every week, for some possible future benefit. I just wanted to add that even in a fat-adapted post-menopausal woman IF may not be so helpful.

    Thanks for your very helpful blog.

  82. Hi Stephanie,
    Very nice article but it appears that you identify IF as primarily caloric restriction. My interpretation of IF, based on evolutionary principles, is very different. The IF I practice is NOT about restricting calories – it’s about WHEN I get my calories & the type of metabolism that I want to maintain. It’s about breaking the insulin/blood glucose roller coaster, lowering insulin levels (caused by too many carbs or proteins in the diet) & optimizing ketotic metabolism. I get all the calories I want & need (satiety based, approx.2200-2800 Kcals) from 2 meals (lunch & late supper) & sometime a late afternoon snack (plus my morning cream). I practice IF daily (5-6 days/wk)… between 9pm to noon…. I do have a cup of coffee w/ 1/4 cup raw cream every morning. When situations present – I may not eat for 16-28 hrs, though I don’t plan this as a routine. I have been in ketosis for nearly 3 yrs. – on a Paleo/ancestral based, very nutrient dense, moderate protein, high fat (70%+ Kcals) program [70% F/ 20% Pro/ 10% Carb]. Prior to this change, on a higher carb (40-60% Kcal) diet, I would become hypoglycemic if off food for 4hrs.

    I lost abdominal & back fat (8# worth) over a 4 month period – while eating 4000kcals/day, on average. I shifted to a bit more “feminine padding” – so a more feminine figure, corrected my high TSH (3.2 down to .77 now), completely cured my “pre-diabetes”, adrenal fatigue & fibromyalgia, gastric issues & eliminated severe menopausal symptoms (I am 54yo)& have great libido again. I am back to exercise training at full capacity w/ short recovery times & good muscle mass development, great REM sleep, calmer with improved brain function.

    I am a clinical physiologist & am following 40+ clients on versions of this program, tracking biometrics/labs/food logs – some are at 2yrs out… What I have observed for success (using food logs), for the majority of both men & women to gain optimal results from a “paleo” program…. 1) The body must be adapted to ketosis as the primary energy metabolism to truly be comfortable with IF – being on a fat based energy metabolism vs. a carb based one. Unfortunately, Paleo based nutrition is not necessarily fat based – but more likely protein/carb based (aka Cordain) and be more problematic for women. And, why many men struggle as well.

    2) Most “problems” come from really poor food choices- even though people think they are eating “paleo”. And that the amount, quality & type of fat is critically important. Without following truly healthy nutritional eating & doing food logs – we fail to identify the correct variable which often leads to dangerous & erroneous generalizations. So Paleo or high fat or low carb or IF …. Are labeled as failures or unhealthy, when it’s really poor food choices that are at cause – both macro & micro nutrient based.

    What I have found is that a wide stratification of animal fats from healthy animals (dairy, beef, mutton, pork, fish) & coconut, etc. is absolutely critical but rarely focused on. With my clients who have problems (hunger, binges, poor sleep, irritability, hypoglycemia, hormone imbalances, etc.) once they correct to a higher fat/better fat quality & wider variety – it resolves most issues (all else being balanced). Based on current research (all of which is very limited due to incorrect assumptions & poor control of the variables) women are very carb sensitive and men tolerate carbs better (Heartwire). So, this would potentially indicate (as might the caloric restriction studies) that fats are a healthier substrate for women, and men as well. High healthy fat/low carb/moderate protein/ nutrient dense paleo is truly worth consideration. Viva Vida!

  83. Great article and a very important topic to cover. In my own independent search I did come across this human trial comparing men and women at 14hr and 22 hr fasting marks.


    Overall it concluded that men and women had similar changes in blood glucose between the fasting times. Plasma epinephrine was increased more in women at 14hr mark, but men had greater changes from 14-22 hr. Glycerol was better increased in men from 14-22 hr, but basal glycerol was higher in women.

    In the end it concludes that:
    “In summary, the results of the present study demonstrate the presence of gender differences in lipid but not glucose kinetics in men and women who were matched on percent body fat. Basal lipolytic rates (assessed by glycerol Ra) were greater in women than in men, whereas whole body glucose production and utilization were similar in both groups. During early fasting, the relative increase in whole body lipolytic rate was blunted in women compared with men, whereas the decline in the rate of glucose production was similar in both genders.”

    Fasting appears to be a better manipulator for increasing FFAs for men, but there are still many factors involved overall. Hormesis is a big player, with overall stress in lifestyle/exercise and even glucose management.

    I don’t advise low carb full time or CR along with any kind of condensed eating window, as it tends to promote “burn out” in both males and females.

    Rather I would suggest fat only in the AM (esp with coconut oil for MCT quick energy). I’d also stay away from milk as it can be an insulin secretagogue. Secret insulin during fasting and you will drive down blood glucose (moodiness, fatigue, etc). You can then also keep a more “ketogenic” state going with a lunch of protein/fat/veggies. If someone is feeling hypoglycemic, then add in fruit. Dinner I aim more for starches and protein (esp after a later workout to make muscles more sensitive to glucose).

    More often than not, people try and do too much with IF, low carb, exercise and so forth. This is just too much stress for a body to act healthy on. CR is also not the goal either. One must find a balance and remember that what works for you is all that matters. There are many factors that can be adjusted for an IF lifestyle (calories overall, cycling carbs, hours of feeding windows…or even not at all). 3 meals a day over 12 hours can work too after all.

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  85. This is a brilliant article. I have dabbled with IF, but started immediately not having control over my food once the eating window opens. That to me was a clear sign that this wasn’t healthy for ME. The hunger wasn’t an issue, since I began to drink coffee, an incredible appetite suppressant. I am a strength/conditioning coach and a certified nutritionist. I design nutrition programs for people all over the world and would never recommend IF for females. The Warrior diet to me is a much better version for females who like “under eating” throughout the day. Naturally we get this high.

    These were my conclusions for at least the female population who chose to dabble with IF and Warrior. Many are still doing it successfully so this is not to say this isn’t right for everyone.
    Lowers Metabolism
    Adrenal Fatigue
    Addicted to not eating and mentally feel that all food will weigh you down
    Lose portion control and natural satiety
    Increase in bingeing and possibly night eating
    Stronger in your workouts, but can have an effect down the line for FEMALES.

    I think fasting once in awhile is great for everyone. To practice it on a regular basis is not something I’d ever recommend or any of my clients and seeing this article from you is a breath of fresh air. Thank you for speaking out. Thank you to all the females for coming out with your experiences. We need to be careful with the different approaches we take with our bodies. It’s clear that we are very different from men. Unless we are trying to be men, then go for it!! 😉 I consider myself a strong female, but I’m still a woman and a mother of 2 that wants to show my kids it’s okay to reach for healthy snacks when you feel hungry.

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  91. Hi all! I have been practicing IF and I’m surprised at the results of the studies. I’ve been following the rules displayed on Leangains.com. The trainer/nutritionist for Leangains recommends a longer feeding window for women (14 hours fasting/10 hours eating) and this has worked for me. But what stuck me with the studies is that they used the same eating window for women as they did for men. Also, the amount of calories they were restricted (40%) could have played a role in the results. At 40% less calories, as a 5’2″ 118lb woman, I’d be incredibly tired and unable to do anything! I hope that there will be studies that just reflect strictly IF, but with a different fasting time since obviously women do not react the same way as men. But that doesn’t mean it should be thrown out completely 🙂

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  95. So, the effects on the only part of my body I care about, the brain, are actually better because I’m a woman, AND it has the added benefit of making me less likely to ruin my own life and someone else’s by passing on my crappy genes?

    This only makes me more keen to take up fasting, I see nothing off-putting in the article at all. 😛

    • The insomnia many women experience is probably not optimal for the brain, no. But to each woman her own… 🙂

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  97. You’re so full of shit. Honestly Stephanie.

    I destroyed you in my response video, just pray nobody finds them, because you’re spreading lies.

  98. Incredibly astute and sincere post. New to your site, but I really appreciate your perspective. Thought I’d butt in to give my experiences.

    I have come to find IF natural to me. I have done it on and off for periods of time for years. It stemmed sort of spontaneously from feeling ill effects from lunchtime eating, preferring the alertness of skipping lunch, and hating that if I ate lunch, unless very small, I had poor appetite at dinnertime. Since my dinner times are more social, I love coming home really hungry.

    I am, perhaps to my long term distress, much more energetic in the daytime, more driven to be active and alert, more creative, more perceptive and have better memory function. My periods are generally regular, albeit if I go through a change in diet (e.g. my routine has recently become more conducive to fasting), it seems to be that which affects regularity for me rather than the fasting itself. Can’t be sure though, but I have at least 4 times in the past IF-ed, lost my period, only to have it return within a month of the change I have often accounted for my period regularity in the past to non restrictive, high calorie consumption during the fasting window, and always gentle on myself about the length the fasting window- not that I honestly over think it really.

    My windows of fasting also tend not to be 16 hours, but more like 8-9 hours. Anymore than that and I will get a strong temporary headache upon eating dinner. This is always avoided so long as I have just something (even if minimal) during the daytime. My fasting window nearly always covers lunch and sometimes breakfast can be light, but I tend to nearly always eat/drink something in the early morning. I don’t always fast, and sometimes eat little small meals to just have something to stave off hunger pangs or light headedness. Like a couple of tbsps of rice say, juice, a small salad, or some pieces of dried fruit. I don’t overdo coffee- maximum two cups, but tends to be just one cup, around 2pm. I do sometimes get strong caffeine withdrawal, without that one cup, which I find is exacerbated by fasting. My diet is predominantly carbohydrate based, because I feel best on that. I recently became familiar with Matt Stone’s and Ray Peats work and ate quite a junk food diet for a while, which was fun, but still apply a few elements to my own diet (lots of fruit sugar, fruit juice, plentiful food and other advice to mitigate coldness/low body temperature) etc. Low body temperature is always my personal warning signal. I sleep exceptionally well on the days I fast, and feel optimal when my fasting period includes a few light snacks or coconut water.

    So all in all, a bit biased to IF. But, always open to listening to my body’s revenge signals. I study biochemistry, so all of this is truly fascinating, and so many women’s experiences are very telling. It could indeed be a detriment to my health, but at present, I am being watchful but intuitive, so IF is still my preference – whether health gurus advise or not.

  99. Men were hunters, women were gatherers. Our female ancestors probably had a habit of grazing all day while collecting nuts, berries and other fruits, vegetables and fungi. I imagine that grazing habit was developed so that we could test potential foods for edibility before bringing them back to camp.

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  102. I just wanted to say thank you for the time and effort you put into researching this. I hope that more studies are done on the effects of IF on woman of all body types and health issues. I have been fasting daily for 3.5 months with a 6-8 hr eating window. I find it very helpful in sticking to a calorie restricted diet for the purpose of weightloss. My weight has dropped from 285lbs to 226lbs and counting. Beyond weightloss I have noticed the following changes in myself whether it be from IF directly, the weightloss itself or another unknown reason- improved energy levels, clearer skin, an increase in menstraul cycle (Have PCOS), I no longer have issues with hypoglycemia (PCOS symptom), it has helped me feel more in control about my calorie intake without feeling completely deprived and I feel really great on the whole both physically and emotionally. While I am aware that everyones body and circumstance are different, I would love to have more significant research available so that people can make more educated decisions. While I appreciate your advice for women to be cautious about IF I hope that rhese woman that are seeking advice can find the right answer and solution in their lives to take them wherever they want to be on their journey. IF is working quite beautifully for me at the moment. I hope that it contiues to do so and that I will remain always open to change if need be.

    • Well well – funny I came to this forum via a google while trying desperately to last until 9:30 at least to break my fast. I can finish my last meal by 6:30 so I reckon it’s a probably not long enough but do-able window. What am I doing? I tried to IF about 2 years ago, did it for ~8 weeks with ) results. Felt like a failure, what am I doing wrong etc. etc. I had post-traumatic stress, adrenal issues, etc. so after reading this blog NO WONDER it didn’t work…hmmm. So yes, what is my motivation? My main motivation is to find an eating method that does not require me weighing and measuring everything that goes into my mouth. Because if I eat like a normal person, I gain weight. Simple as that. I am 5’1″ 55kg (120lbs) And yes, like pretty much everyone else here, I have PCOS as well (which I have controlled via low carbing for nearly 13 years! Yes I must have been one of the first to have made the connection, lived with 3-4 periods a year for 15 years, only to have it come back the month after understanding what carbs were and how they effected me….gah why oh why are we not educated on this stuff??? could save SO MUCH heartache and confusion)so I am a bundle of hormonal confusion 😉 I am also a non-competitive body builder. I lift 3-4 days a week and do HIIT ~2 times per week. Have had periods of 10-12 hours a week, now down to a much more realistic 5-6 hours. I will not stop this because I love it; but I also have to fuel it. OK so I have been on a high fat protocol for about 6 weeks. Have gained 2 lbs so am trying to even things out. This week started on bulletproof coffee following fasted early AM (5:30AM) lifting or intervals. Not bad – not bad at all – have the BP coffee around 7:30, but am starving by 9….should I persevere, or is this just dumb? Also just did my first refeed yesterday (after 6 weeks – will do these at least every 2 weeks from here on ~100g rice or sweet potato) and did a great poo this morning! hehe. I am just desperate to find a way to live a normal life where I am not obsessing on food but not gaining weight. It’s so dumb, and frustrating. hmmm. Thanks for listening.

      • I think your last comment might possibly never happen.
        The only way my obsession ever stopped, and period came back was stopping exercise, eating whatever I wanted (including ice cream and cookies) and never looking back.
        Oh yeah, after three weeks of that, I got my first period back in years. I did not have PCOS. I was starving.
        You know how you think “Damn, that girl is so skinny and gets to eat whatever she wants…”
        You can eat whatever you want to, and should. You just might not be built to be ‘skinny.’
        I did gain weight for all this. 40 lbs to be exact. But frankly, I look pretty realistic these days and have my sanity back. It has taken a LOT of therapy to get over my body image issues, that are perpetuated by cross fit, IF, HIIT, paleo whatever. I thought it was my safe haven…that I wouldn’t be “fat’ if I followed it right. But that’s not really true. Spend some hours with set point theory, treat yourself right, take a break…
        and of course if this all sounds scary and horrific to you, I’d consider realigning your goals and seeking counseling. I say this as tenderly as possible, as I have spent 14 years with an eating disorder. And no, by media viewpoints, I was not even underweight, nor had extreme activities. I convinced myself for years it was normal to fight my exhaustion, hunger, anxiety, and obsession with food, diet and exercise to remain a ‘normal’ weight.
        Finally, I wanted to stop fighting that. I gained self-worth and supported myself with good people. Now I can eat a salad or a donut whenever I want, do yoga if it feels good, stay active, and USE MY BRAIN.
        I’m rooting for you!

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  104. First of all, excellent article! Thank you so much for looking into this. I do have a question re different IF patterns. I am a 40 yo female at my happy weight (120, 19% bf). Per a few articles I have read, am experimenting with IF as a 24 hour fast 1 day per week. The goal is not weight loss, but to reap the potential benefits of cellular regeneration and long term cognition. I have been doing this for about 6 weeks, and eating normally on other days (which for me means lots of seeds, nuts, whole grains, fruits, lean meats and LOTS of veggies; caloric intake tailored to make sure I’m replacing calories burned through exercise). So far, I haven’t noticed any particular changes at all, although given my goals, I do not know that I would. Weight, menses, etc. normal, and I sleep like a log, as always. Thoughts? Anyone else on a similar regimen?

  105. From a biological standpoint, this makes sense to me. If a woman has no food or irregular access to it, she can’t reliably supply the nutrients for building a healthy baby, so the body puts the brakes on babymaking.

    This is a good reference to have. I’ve wondered if I was really “doing it right” if I wasn’t inclined to IF.

  106. This is such a great post and such a great site. I was just diagnosed with PCOS a few weeks ago and have been reading your site page to page (trying!!). It’s funny – I started IF (24 hours, once a week) a month ago – before even being diagnosed with PCOS. I’m not overweight at all – but have taken years to get off any easily gained weight. YEARS. Just four weeks ago, I started limiting my grains/carbs, upping my healthy fats, and started doing IF. I instantly have leaned out, don’t have a problem with sleep, and have gotten my period again (after months without). I have seen an increase in some facial hair though (even though that has always been a problem and seems to fluctuate). Do you think that this is therefore something I should continue, due to the results so far? Reading this article does scare me a bit – but seems like it is starting to do some good things to my body (ie getting my period, leaning out, etc). Thanks so much!

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  108. I’d be extremely skeptical of using rat studies to draw conclusions about humans when it comes to fertility.

    The human and rat reproductive strategies are completely different. Humans have 1 or 2 babies per year. Rats gestate in 3-4 weeks, have up to a dozen babies in expectation that half of them will die, and are ready to be impregnated within 72 hours of delivery.

    OBVIOUSLY female rats would get a little freaked out if there weren’t food around for a few hours… because their lives run at 1/16 of human scale. If you were a rat and you didn’t have food available, and were faced with the prospect of generating 10 ratlings in 3 weeks, I’m sure you’d shut that whole thing down until you found food, too. And I’m sure it would stress you out.

    Humans, on the other hand, have a reproductive system that’s extremely tolerant of the metabolic up/down regulations that happen in the face of more/less macronutrients.

    It HAS to work that way. Otherwise we’d miscarry whenever the hunt didn’t go so well, and that would be a ridiculous and needless expense of energy.

    I’m not trying to discount anecdotal reports of IF not going so well for women. I have no doubts that IF is not for everyone.

    But let’s at least start looking at the actual reasons why, and not throwing the baby out with the bathwater.

    For instance, most women try to do a low-fat / high-protein / moderate carb version of IF for whatever reason. And that is disastrous for hormones for women, absolutely.


    a woman who has been very successfully IFing for over a year on a high-fat / moderate protein / carbs-only-after-training diet, and got pregnant the first time she didn’t use protection.

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  112. I’m not paleo- I guess I’d call my ancestral diet the “nomadic herder”. I get most of my calories from raw grassfed cream, kefir, and butter, with the remainder from fatty meat and the occasional carb. Not too much veg and little fruit. I really just did a ton of research and trial and error, and found what worked for me. Interestingly, I drifted into IF organically before I ever heard of it: I generally have a good lot of very thick cream in my coffee in the early morning, then do yoga for several hours, and have a large glass of kefir around 1 or 2 pm. I typically eat “solid food” between 3-8. I guess this isn’t “proper” IF, because I get calories all day- closer to Dave Asprey’s bulletproof coffee idea. But I reap huge benefits in terms of resting my digestive tract. I do advanced pranayama and yoga asana, and I just really cannot have a bunch of food making its way through my body all the time. That’s why I rely on really calorie-and-nutrient-dense, highly-digestible foods. I feel great, NEVER get hungry (I eat when I’m hungry, not negotiable), and you could set your watch by my period. So maybe a modified fasting regimen, with a few hundred calories of saturated fat in the a.m. makes more sense for women? Btw, I am not skinny, or even a little bit eating-disordered. I’m a chef, and I eat like one.

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  116. Oh my…I just went to the doctor on Monday to get a bunch of bloodwork done (no results yet) and all week long I’ve been wondering what on earth is wrong with me. Excess androgen, insulin resistance, pre-diabetes, PCOS? I never even thought about the fact that I am basically starving myself everyday and that THAT could be effecting my hormone levels. I don’t ever intentionally IF. I eat about 7pm and then if I’m hungry might eat around 1Oam, but for about the past 6 months or so I’ve been eating closer to 2pm. The reason I went to the doctor was because my face, chest and back have been breaking out like crazy! Cystic acne like I haven’t had since I was a teenager. After reading your article I immediately ran to the kitchen to heat up dinner (which I wasn’t going to eat) and made myself breakfast for tomorrow. I’m crossing my fingers that by making a concerted effort to eat breakfast I’ll be doing myself (and my skin) a major favor! Thank you!!!

    • Hooray! Oh, Brooke, I’m so happy. I really do think this will help you. It takes a long time for hormones to really fall in line, but progress does happen day by day. 🙂

      Best of luck to you, and my blessings and empathy for your acne.

  117. I started IF this month and noticed my period was late for the first time. I’d like to understand the effects better as my wedd

  118. I started IF this month and noticed my period was late for the first time. I immediately stopped the diet, though I’m disappointed as it seemed very promising. I’d like to look into the endocrine masculinization effect, particularly, – does it lower estrogen levels, thereby increasing the testosterone to estrogen ratio? My wedding is soon and I’m crunched for time so I suppose I’ll have to resort to exercising for hours.

  119. Thanks for the info. Im overweight and find IF works for, so Im going to continue.
    I IF 3x per week by eating a large lunch and then not eating again until breakfast the next day. I find its quite easy to do, I have more energy, my weight is shifting and I feel much clearer in thoguht, I sleep well and my periods have remained normal.
    If at any stage my body starts sending me signals that I am placing it under undue stress or there is a negative reaction to this I will stop, but for now this seems to work for me in conjunction with a paleo lifestyle.
    Thank you for the food for thought…

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  122. My toxic ex-boyfriend used to try to get me to fast so I would suit his aesthetic. I dumped him, of course. I’ve never been a fan of fasting.

    But on the Autoimmune Protocol, I’ve found that sometimes I simply do not want to eat for a while-sometimes 12 hours! I am hoping, since I am about 40 pounds overweight, that this is simply my body’s signal to back off because I don’t need the calories…I’m hoping that it’s my metabolism healing right
    along with my gut and kidneys and pancreas and everything else…

    • I didn’t have time to read all the comments to see if someone had already posted this link and couldn’t find any obvious way to email you, so if I’m repeating stuff already posted, my apologies.

      The following article was published in the British press – a medical and TV doctory has been widely promoting the 5:2 fasting diet and this article draws attention to the dangers for women:

      I think I’ve posted this link on another post, but I think it bears repeating:

      There is some evidence that while fasting can have excellent effects for men, the effects on women can be detrimental, especially pre-menopausal women. I’d suggest anyone thinking about trying it read the following blogpost:


      Two particular concerns are that women (a) “did not experience increased insulin sensitivity” and (b) “actually experienced a decrease in glucose tolerance” which don’t sound like particularly good things for Type 2’s.

      There is also another article that specifically refers to the 5:2 fasting diet and women here:



  123. Very interesting read. So far I always thought that intermittent fasting was also an excellent way to lose weight for women. I know Martin Berkhan recommends shorter fasting periods for women compared to men.

    For me it has certainly done wonders. Lost more than 40 pounds since I started intermittent fasting.

  124. This is a very interesting piece of work from the perspective of sex differences to dietary interventions; in this case fasting. I would be very interested to know what kind of fasting the women whose results indicated a potentially harmful effect were performing. There are different methods of fasting – water fasting, once considered to be the pinnacle, is no longer recommended by many (myself included) since most people are far too nutritionally depleted for it to be sustainable. I favour low glycaemic juice fasting. This is the method used by the Hippocrates Health Institute for both sexes, with remarkable success. As long as the blood sugar is maintained at a stable level by using protein-rich sprouted foods in the juice, such as sunflower and pea green sprouts, there seem to be only beneficial results, once the people who should not fast at all are accounted for (unstable diabetics, people more than 10lbs underweight, pregnant or nursing mothers and a few others that I mention in my book and other articles on fasting that have been published in UK health magazines).
    It would be fascinating to test women on these regimes in a well-planned and rigorously controlled study. I, for one, would be happy to be involved in this.

  125. Here’s what I take away from the rat study: fasting will make me smarter and more energetic while keeping my girly bits from continuing to be a moody, bleedy drain on the parts of my system that actually help me function.

    And the downside is?

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  127. Stefani,

    “Extraordinary claims require extraordinary evidence” -Sagan

    IMO, you are a victim of confirmation bias(whether or not you are correct).

    This is an interesting blog though, thanks for your time.

    • I don’t think this is an extraordinary claim at all — I advise caution and a reservation of judgment in the post.

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  137. Hello,
    I’m doing the 8-hour eating window idea, with 16-hour fast periods. Since 1/7, I’ve lost 6 pounds (started at 161#, 5’5″; as of 2/1 am 155#) and at least 2.5″ off my waist.
    I’m in my early 30s and very healthy, other than the excess body fat. I have followed nationally (i.e., not Paleo-) recommended nutritional guidelines: no more than 35% fat per day; more than 25g fiber; more than 45 g. protein. As weight loss is my goal, I am trying to eat between 1,200 – 1,300 calories per day, between 11 a.m. – 7 p.m, in order to achieve a 1,000 calorie daily deficit, but if I’m truly hungry, I eat more. However, I’m not hungry – ever; this has taught me to listen to my body and stop eating. There have been days I’ve had to eat more in order to ensure I’m at least getting the 1,200. I’ve found this to be very easy – I’m not hungry, am more mindful, losing weight at a reasonable pace, and am not at all irritable. My period came as expected a week after starting the diet, and is due again in 10 days. If there’s a delay, I’ll check back in and report.
    I read this article and every comment with interest, in order to assess whether I should shift and try the 5:2 diet as advocated by Dr.Michael Mosely, since I want to improve my health beyond weight loss [5 days eating normally, about 2k calories daily; 2 non-consecutive days eating 500 cals]. I will try it for a few weeks, but will abandon it if my body doesn’t respond well. Thanks, all, for your comments. It’s so helpful to have peers check in with their results.
    My goal is find a lifestyle that is aligned with my natural impulses and comfort needs, so I’m not interested in taking severe measures long-term. “Severe”, as I define it, would be true fasts (no food for 24-hours) once a week or more, or a serious imbalance in the nutritional proportions as defined above. Good luck to all!

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  139. I posted a bit further up the thread, ralking about the fact that I had been doing a 24 hour fast once a week, not to lose weight but for the other benefits of fasting. Just wanted to report, for anecdotal purposes, that I have now stopped. As I said in my post, I did not see any weight or body mass changes. On the flip side, however, about six weeks after starting weekly IF, my immune system CRASHED. Up until that point, I hadn’t had any illness to speak of for years. IF was the only major factor in my life that changed — no additional stress or other life changes. I am now back to where I want to be, healthwise, but it took a while for me to get my feet back under me. I will not be doing IF again.

  140. How safe and effective is intermittent fasting for PCOS sufferers?

    I have PCOS, am 30kg overweight, I have excess oestrogen, excess testosterone, hirsutism, irregular and heavy menses, and Endometriosis.

    Overcoming all of these issues feels like an impossibility!

    • I have thoroughly appreciated the article and all the informative comments. When I got to yours, I felt compelled to respond as I have suffered forever with severe cramps during the first couple days of my period, I cannot take pain medication for various reasons, and I found relief by fasting (quite by accident!). This is somewhat off topic as it has nothing to do with IF or fasting as a regular habit. I just found by accident once that when I didn’t eat, my cramps went away. Away. Totally. I thought it might be a fluke, so the following month I fasted again. Same thing. I have been doing this for many months and I’m so relieved. I do not know if the cramps going away is due to simply not having the bulk of food moving through my digestive tract at that time or what.

      Try this: I get up in the morning (assuming I just got my period the night before) and I mix 1 tsp of organic blackstrap molasses in hot water and sip. (It is full of many vital nutrients you need while menstruating.) Throughout the day, I will make that several times and in between I drink lots of water. After a couple of hours the cramps go away. I usually finish my day with a small meal around 5:30 (at which point the cramps come back) and then do the same thing again the next day. As I said, my cramps only last two days so this is only 2 days out of the month and I’m still supporting my body with the molasses. But my cramps used to be excruciating, and I no longer dread getting my period.

      I sincerely hope this helps.

      I do not know if fasting of any kind would help your other issues.

      Take care!

  141. I’ll just “weigh” in on my own experience. I do an alternate day fasting (ADF). It’s as simple as it sounds. Eat one day (what you like) and fast the next. It’s not a complete fast, I drink veg. juice that I make, totalling a few hundred calories for the day. I’ve had insomnia for 20 years, have done menopause and can tell you that my sleep, my hunger signals, everything has improved by eating this way. I’ve tried the other daily window types of IF and, meh. Not for me. There’s tons of longevity proof out there for drinking homemade veg. juice and ADF.

  142. Have you considered/reviewed the following two studies:

    “‘The effects of intermittent or continuous energy restriction on weight loss and metabolic disease risk markers: a randomized trial in young overweight women: Randomized comparison of a 25% energy restriction as IER (B2710 kJ/day for 2 days/week) or CER (B6276 kJ/day for 7 days/week) in 107 overweight or obese premenopausal women observed over a period of 6 months.”

    “‘Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women.’ This study examined the effects of IF plus CR (with or without a liquid diet) on body weight, body composition, and CHD risk. Methods: Obese women (n = 54) were randomized to either the IFCR-liquid (IFCR-L) or IFCR-food based (IFCR-F) diet. The trial had two phases: 1) 2-week weight maintenance period, and 2) 8-week weight loss period.”

  143. My period has become irregular for a while since I started heavy training and dieting to cut body fat. I started 24 hour once a week fasting last September. It certainly helped with my productivity on the fast days. However, I consistently wake up at 4 AM (mid-way into my sleep) very bewildered, have to eat and take hours to calm myself down before I can fall asleep again. Hence, when I fasted on Sundays, Mondays were pooped days for me.

    I certainly didn’t get leaner so it wasn’t helpful with even maintaining my body composition. I got off IF eventually and now having to work to fix my hormonal issues.

    I’m not sure if IF contributed to my latest eczema breakout (because of the adrenal/stress connection) as the breakout was about a month after I started regularly fasting. However, because the symptoms significantly improved by the end of the fast days, I realized then that food allergies was a big contributor and, although it may mess up other things, fasting help with food allergies.

  144. Great article, Stefani. I came across it a while ago and bookmarked it to come back to later, which I have a couple of times.

    Today I came across this study, which may be of interest to you and your readers: Impact of binge eating on metabolic and leptin dynamics in normal young women — http://www.ncbi.nlm.nih.gov/pubmed/10022396

    The researchers found that “1) ingestion of a large number of calories at one time (binge eating) impacts metabolic parameters even when total calories and macronutrients are appropriate for weight; 2) the timing of energy intake is an independent determinant of the diurnal rhythm of leptin secretion, indicating a relatively acute affect of energy balance on leptin dynamics; 3) the mechanism of exaggerated insulin secretion after a binge meal remains to be determined, but may be related to the altered diurnal pattern of leptin secretion; and 4) as most binge eating episodes in the population are associated with the ingestion of excess calories, it is hypothesized that binge eating behavior is associated with even greater metabolic dysfunction than that described herein.”

  145. I’ve been IF ing daily for the last 3 months. I am an athlete and I train 5-6 days a week, high intensity kind of stuff. I have always had to fight to stay lean, even eating a clean, Paleo diet. The IF ing has been a game changer: I’m leaner, more alert, a better athlete (stronger and faster), I sleep better, the list goes on…..

    I will probably never go back. Intuitively, I feel like IF ing allows your body to look and feel the way it is supposed to. Also, there is some sort of magic that happens when I train fasted. And then when I do eat, I really appreciate the food.

    On top of all that, it is such a relief to not be a slave to food. You really learn a lot about yourself…..like when you are REALLY hungry, and when you are encountering a meaningless craving.

    I can’t say enough good things about IF. I really don’t think women should be so freaked out by it. I started with a 16/8 protocol but that got pushed to more of a 20/4 schedule (without even trying, that’s just what feels best).

  146. PLEASE HELP!!!!!! I’m an interesting enigma. Who wants to solve it?!? (thank God I found this site)

    So I’ve been doing IF for the past 3 months. The first 2 months I was doing the Insanity 60 day challenge, which I know is not too favored in this line of primal thought. But in those 2 months, I lost 3 inches of belly fat. Yes, it’s a very slow progress, but at this point I’m used to slow progress like that with my body. I just don’t lose weight quick (I’ve been working out for 2 years before I did the Insanity challenge, so I didn’t go from couch potato to the challenge. I have already seen significant weight loss, but I’m missing 25-30lbs to be gone… I’ve lost a total of about 60 lbs in about 1.5 years. Suuuuper slow. But I’ve done it all myself, naturally, lots of trial and error and doing every workout video in existence)

    I’m 25. Female. Current weight: 160. 5’3″.
    Yes. Sounds like I’m a chubby one, but I think it’s safe to say I have a good 5-6 lbs of hard earned muscle. My thighs are basically ripped, my arms are strong (although there’s still fat around it. ugh). Underneath my belly, I know that my abs are strong and present cuz I have pretty good core strength. My resting heart rate is in the 60s. I’m doing The Asylum now (which is crazier than Insanity). All in all, I’ve been training like an athlete, and I feel strong and fit. I do weight training about 3 days a week too and I lift as heavy as I can.

    But I’m overweight still. I don’t understand why. I do IF, I drink almost a gallon of water a day, I workout while I’m in a fasted state and eat like 2 hours after I’m done working out. My eating window is like 6-8 hours every day. I do not eat white rice, or pasta, or bread. My meals usually consists of oatmeal (with chia seeds, flax seeds, some nuts, berries, almond milk some times), big bowls of salad (spinach, kale) with olive oil and vinegar dressing, beans (seasoned with herbs and all natural stuff), shredded wheat cereal from Trader Joes (which I think I should stop consuming actually), greek yogurt sometimes, butternut squash, and my guilty pleasure, this whole wheat homemade bread my mom makes with flax seeds and nuts. It’s delicious. And it’s nutritious but it’s carbs nonetheless. Sigh. Still I don’t eat it every single day. And if I do it’s no more than a slice. I barely eat meat, and when I do it’s chicken or turkey. I don’t drink soda coffee, nor juices. I drink green tea, no sugar, everyday. All sounds pretty decent right? For someone who exercises as much as I do, I should be skinny minnie.

    This past month I fasted for 24 hours, twice, one week apart. And I also did the P90X and The Asylum hybrid work out… I burned 11,400 calories (heart rate monitor) this past month… and guess what? I did not lose a single inch. Never mind weight on the scale. I don’t care about that. But when I measured myself and saw no progress I wanted to curl up in a ball and disappear. And btw, when my ovulation came around I was secreting all kinds of dark brown fluids for a whole week. And even tho that could be normal-ish, it just felt odd in my gut. After reading here, it might be the IF messing with my hormones.

    So ok. As a woman, and probably cuz of hormonal issues (I was diagnosed with PCOS in early 2009. Back then I was 60lbs heavier. Haven’t checked my PCOS since then. ) I lose weight very slowly. Plus I sorta stress about it alot. I get it. But it just doesn’t make sense. Why is my body holding on to fat that isn’t good for it anyway!?
    I lost inches those first 2 months, but I really expected to lose some more this last month. So that means, I plateaued. What do I do? Do I eat more? I don’t want to!
    Do I rest for a week? (Please don’t tell me to do that. I’ll go crazy) I just don’t know. Help me please.

    My goal is for a month from now to be 3-4 inches thinner. I set this goal months ago. I don’t know what I’ll do if I don’t reach it.

    My current measurements are:
    Waist (as in the curve part) 33″
    Belly (right at the bellybutton) 35″
    Chest: 37″
    Hips: 39″
    Arms: 12″

    My goal:
    About 2-4 inches less of each body part.
    I’d be happy with a 29-30″ waist. I wanna look strong not necessarily super lean, altho that’d be nice, but I feel like it’s too much to ask =/

    Thank you. Help me please since I’m considering that HCG diet just to be thinner. Save me?

    • Hi,

      Sounds like you are having a very frustrating time! I’ve experienced a few similar issues and have a few suggestions.

      Firstly, working out as much as you do is fantastic but don’t let yourself fall into thinking that it earns you extra calories to eat. I used to do a tough workout 3 times a week: HIIT and weight lifting workouts ( I don’t believe in cardio). But I used to think that I could then consume more calories so I ended up gaining a lot more weight… then I made excuses to myself about ‘muscle being heavier than fat’ but that’s just me! 😀

      Secondly, if you feel like you have plateaued, try calorie cycling. Keep your metabolism on it’s toes. Whenever I’ve found that I’ve stopped losing fat, I spice things up a bit. E.g. do a 36 hour fast then get back into routine again.

      Thirdly, your diet sounds healthy but with all the seeds, nuts and olive oil it is really easy to lose track of calories. I love the Paleo diet BUT fats are so much more calorie dense than carbs and protein. I’m not saying eat more carbs at all but try to count/measure your calories in the nuts, seeds and oil. Have high protein, little fat and no carb meals. I got a little carried away with paleo when I first started, thinking nuts are natural healthy sources of fat. Whilst they are nutritious they are also very high calorie.

      Finally, IF is a useful tool but it completely depends on your body and how you react to it. It’s completely a trial and error thing and you just have to figure out what works for you. I’ve tried various fasts: 2 x 36 hour fasts per week, 20 – 4, 16 – 8 etc. All of them have affected my periods in some way. I have now settled on a routine where I only fast for 14 hours a day, this seems to work for me. I use IF to help me keep track of my calories, it makes the rules simpler.

      If you find IF is not working or is effecting you in undesirable ways then simply take a break from it and come back again in a couple of weeks with a revised routine.

      I really hope I’ve been useful. It’s so hard to tell what will work for someone else, I can only tell you what I’ve learned and try to help. Good luck!! 😀

    • Hi, Ginel,

      have you checked your thyroid function? Underworking thyroid makes us put weight on. I am sure there are plenty other genuine medical reasons making it hard to lose weight.

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  149. Interesting discussion, thank you. No question that women respond differently to men to intermittent fasting, but in my clinical experience, it doesn’t mean that they cannot do it. They just must be aware of what is happening in their nervous system and HPA (adrenal) axis. Very stressed women should not attempt fasting, as it will disrupt their sleep and female hormones. But calm women can attempt it on a calm day. Fast can be shorter, say 10 hours. And remember that gentle carbohydrates promote relaxation and sleep, so they can be used strategically in the evening meal before the fast.

    • I support the point relating to stress. I do not fast and deliberately do not as for me the balance of blood sugar is so crucial to my mental and physical health that fasting simply does not work for me and makes me then over eat later. My body likes the assurance of 3 healthy meals a day without snacks – in a sense that is a form of fast – I make sure I do not graze all day but without the stress of fasting.

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  152. Thanks for this! My fiance is a fitness coach, and he RAVES about this IF stuff. I finally decided to try it, and he did say that women only have about a 45% chance success with it. We’re just not meant to run that way…
    He also said, if you want to try it, women should NEVER go over 14 hours without eating. I’m trying the 12/12 to see how it goes. So far I’m just a bit more tired than usual. But definitely good to know it’s not just me, and that I shouldn’t stick with it if it doesn’t feel right! He has dropped 30 lbs though! Jealous….

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  154. Hi,

    As a muslim I’ve been encouraged to fast twice a week (mondays and thursdays), which I had been doing all my life until university started and fasting took a back seat to girlfriend lunches. Ive always been healthy and had never really worked out per say though I go hiking perhaps once a week or two weeks.. but a month after I stopped fasting I realized I was feeling more tired than I did usually, and anther month later not only was I putting on a weight but started having shorter periods. After hearing about IF i decided to get back in shape in a short time and started doing a 16 hr fast everyday but that just left me more drained and took my PCOS out of control. No surprise I stopped. But few months later I started fasting twice a week again (though this was more of a religious decision rather than a diet trick), I was flabbergasted at how quickly i lost weight, PCOS was back under control, i felt as alert and energetic as I did when I was 18..needless to say I’m going to stick to this forever now.. but this really proved to me that there IS a lot of truth to the benefits of IF, but it really depends on what works for the particular person.. but finding what works surely must be the biggest challenge..

    • Culture and fasting is fascinating. In my religion Catholicism Friday used to be a day of fasting and still is for some, every week. That is why in English schools they still have fish and chips for lunch on Fridays as it ended up changing from a fast to no meat on Fridays so people all ate fish instead. Most of these traditions go back to neolithic life 2000 years ago so there is usually a living in the “desert” or other reason behind them.

      “IF” is not being used well in the UK at present, though in the current craze. There seem to be a lot of people eating any types of bad foods all week and then easing up on two days. Of course that is going to be better than stuffing yourself with junk food 7 rather than just 5 days a week but I suspect many of those people would be better changing to better foods 7 days a week and not fasting at all.

      [Or perhaps that is just my excuse because I cannot fast]

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  157. I am endo-meso and was mostly Paleo last year (I would eat a treat grain or two once a month). I did IF (20-4) once for about two weeks and lost about 10 but slowly gained 7 back. In 2013 I went totally grain and gluten free. I went back to IF in January and again lost about 8 lbs right away so I decided to stick with it and just eat one main meal a day. I was only 10lb from my dream weight so I decided to up the ante on exercise and did 2 heavy weight workouts and one day of sprints that week. Almost overnight I gained 12 pounds and the scale has continued to creep up so now I’ve gained 18-19 lbs!!! I figured some of it was glycogen but it’s worrying me that it hasn’t gone away. My time of the month has also been a nightmare since doing Paleo. It’s worse and longer. Everything else is great! My skin looks amazing, but the fat and cramps are unbearable!!!

    • I have been through what you have. I’d guess that your body is beyond stressed. I hold on to 10-15 lbs when stressed even though I’m eating clean. Over the years I have tried ESE style fasting, alternate day fasting and 8 hour eating/16 hour fasting (and I did all of these for periods of at least 6 weeks to see how I fared) I also worked out with a moderate-high intensity 5x per week. I slimmed down but hit a plateau. Now, I fast daily but I do a 10 hour feed window (give or take) It works best for me. I wake up and drink coffee with some fat that is usually coconut oil, butter or cream. Then I have real breakfast at like noon. During my window I eat primally. I specify primal cause I love me some dairy 🙂 I am lame and wear a pedometer and make sure that I hit at least 10k steps a day (or i get on my mini trampoline and go to work) and I do tabata style exercises 2x per week. Anyways, sorry for all of the detail but this regimen has allowed me to be at my best and most easily maintained body ever. I guess I’m saying don’t be afraid to change it up… rigidity isn’t always the answer.

  158. Chiming in to say I started IF a few weeks ago after watching the Mosley/BBC documentary. (5:2 – 2x a week, 500cal dinner only. I drink loads of green and herbal teas thru the day until then, then right before dinner I usually make a cup of organic broth just for something savoury. My boyfriend has much less to lose but was curious to try it to improve muscle definition in his abdomen (the only place he needed to really lose anything). In the evening, I prepare a 500 calorie meal, always lowcarb (tonight for instance was spinach, tomato and cucumber salad with balsalmic dressing and grilled halloumi), and my SO has his with extra crispbreads or portions to add the additional 100 for men.

    As for me, I’d previously lost about 21kg (50ish pounds, I believe?) over two years of what I’d say was lowcarb/primarily paleo eating (I say “primarily” because I did continue to eat organic yoghurt almost daily and relied on the odd Atkins bar when in a bind)….but weight loss had stalled after 21kgs, and I have felt – even though I’ve kept it off – that I needed to shake things up a bit. I also felt I was eating healthy calories overall, but still too many of them. (I don’t eat junk food and I rarely touch sugar or wheat – but calorically its easy for me to get too many, since many beneficial foods that I rely on – coconut oil, macadamia nuts for instance – are not exactly low-calorie. I take a few supplements daily (based on the Jaminets’ “Perfect Health” recs – Vitamin D and K2, a B complex, a probiotic, Magnesium, Copper, etc).

    Still – I feel these choices laid a good foundation for IF, because I don’t have issues with blood sugar “crashes”, headaches, I sleep very well if not better since I started this…..so when I see irritability/headaches/blood sugar crashes being described by people for whom it’s not working, I would only question if that could be in part due to nutritional deficiencies or bad diets.

    I see a few stories now and then about people who experienced some issues like this – but then in the same story talk about the gorging on “feed” days, describe junky or carby meals, etc – and I have to wonder if IF has gotten a bad rap when in truth, other factors can be the root cause. I feel like my body isn’t needing anything because nutritionally, I’ve given it what it needs and fuel-wise, it’s already fat-adjusted and not seeking carbs for a quick fix.

    Of course, we’re all different, and I know what works for one won’t for another – but I for one find the research compelling not just for weight loss but improving quality of life as we age and as long as I’m feeling better on it, and feeling my body streamline somewhat, I’m all for it.

    For my part I’m in my 40s, have about 13kg (30 lbs or so?) left to lose and IF has, at least so far, been not that hard at all.

    For what it’s worth, my 2p/tips:

    I deliberately choose my 2 busiest days to fast until the small dinner meal, Tues and Thurs

    I keep lots of herbal and green teas around to enjoy through the day – helps me stay hydrated, keeps my taste buds entertained.

    I have a cup of 5cal broth before the evening meal, takes that edge off if I’m hungry so I don’t eat too quickly, and it tastes surprisingly good.

    On my “feeding” days I make an effort to eat normally and I actually use an app to track calories even on THOSE days so I am sure I have a “feel” for what my suggested goals actually amounts to.

    on Wednesday and Saturdays, we opt for more indulgent foods but keep the day’s food within an 8 hr window and usually just have 2 meals that day.

  159. Hi Stephani, awesome article. Having suffered with disordered eating for years I can definitely relate to the ‘high’ described above whilst fasting. I feel like part of the high came from my perverted self-‘pride’ that I had managed to survive without food for a few hours….

    What do you think of the IF advocated by Dave at the bulletproof exec? i.e. having the bulletproof coffee (coffee, butter & MCT oil) for breakfast? how essential is the protein?

    • I don’t like it all that much, to be honest. Dave claims that eating MCT oil prevents adrenal stress, but I’m on the fence on that one. I think at least some protein or carbohydrate is the best way to tell a body it’s been fed. Fat rather flies under the radar in that regard.

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  165. I started fasting one day a week about a month ago and eating about 500-700 one other day out of the week to lose 5 lbs. I usually eat around 1800-2200 calories on the other days and work out for an 1hr and sometimes two hours 4-5x/week. I didn’t think i was going to have a late period but I am now 1 week late!! This is frustrating because im actually eating way more with the fasting than when i ate everyday. I average only 1400-1600/day.

  166. Caloric restriction may have its evolutionary roots as a survival mechanism, allowing species to survive on scraps when food is scarce in order to continue to reproduce. But that restriction only has lasting positive effects if the overall diet is a balanced one, which may not always be the case in conditions of famine. (That also explains why anorexia is so unhealthy: people who starve themselves become malnourished). It’s possible the strategy developed as a way to protect species from consuming toxic plants or foods, when it wasn’t always obvious which sources were verboten.;;^*

    Check out our homepage as well http://caramoan.co/index.php/

  167. I have been doing 16-hour fasts since April 2012, and it helped me lose and maintain my weight. I found that I get hungry only after I eat not during the fast, but I do eat as much as I want during my feeding period.

    I did lose some of my hair doing it, along with a rigorous exercise regimen. What helped regrow the strands was a daily intake of multivitamins with iron. As to menstruation, I found out that fenugreek helped regulate my period and relieve the symptoms that come with it.

    I don’t have problems sleeping either because of it. Oftentimes, if ever I sleep late, it’s because I couldn’t stop reading articles online.

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  170. “Many women find that with intermittent fasting comes sleeplessness, anxiety, and irregular periods, among a myriad of other symptoms hormone dysregulations.”

    It sounds like these women are suffering a healing crisis, or perhaps Candida die-off.

    I am an overweight, formerly insulin resistant woman in the middle (6 weeks into) my own 90 day challenge trying IF. My head is clear, I have better focus, I actually feel like I *have* a metabolism for the first time in decades. I have no hunger, no cravings. My insulin resistance is broken. I fast 18 hours a day, and eat 2 meals in 6 hours. I have no desire to snack. I have no desire to ever go back to the way I was eating before. I had been doing a 12 hour daily fast for the last year which stopped my hunger and cravings but did little else. When I ramped it up to 18 hours, everything changed. Cravings dropped seriously in the first 24 hours, and were gone in 48. No hunger. I eat 2 meals a day and have no desire for or interest in snacking.

    No one should pass judgment on IF without TRYING it in a serious manner. A few hours here and a few hours there, erratic attempts won’t show them anything.

  171. What a great article Stephani. Only on Wikipedia have I ever seen such thorough referencing/footnoting!!!

    I have been If’ing for about a month now in hopes to lose 30 pounds, which I clinically need to lose. Have not lost any weight, even though in addition to the IF’nig I just joined a gym and have gone 7 out of the last 8 days.

    I have experienced this strange phenomenon starting in the last few days, that when I look at myself in the mirror, I feel that I look less “pretty” or less “girly”. As your article may indicate, it could be that my male hormones are taking over! Exercising for the first time in almost 10 years may have something to do with it too.

    I look forward to reading more of your posts. Thank you again for your dedication!!

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  178. Thank you for this article!

    So happy I found this website! I am not strictly Paleo, but find that my diet is quite similar. It’s just great to have a website dedicated to nutrition as it specifically relates to women. Yay!
    I did IF for almost a month and my period is currently one week late. (And doesn’t seem to be hurrying anywhere. Haha!)

    Thank you again for the article!!



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  180. Thank you for this article. It was a really interesting to read. I personally love IF. I fast for a full 24 hours 2 – 3 times a week and feel really energised and mentally clear. Guess I’m just lucky.

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  183. Hi Stefani,

    Wow this was like a kerching moment for me when I found your blog today and of why possibly 5:2 Intermittent Fasting has NOT worked for me for over 6 months on and off. I was convinced there was something terribly wrong with me and put it down to my metabolism being stuffed after quitting smoking just under 6 months ago and my age. But maybe just maybe it was just down to the simple fact that fasting DOES NOT work for every single person on this planet. I have felt so frustrated and so angry at myself for not losing any weight and been made to feel a fool because everybody knows it’s calories in and calories out and if you are not losing weight by fasting you must be doing something wrong right?

    I have basically gone Paleo/Atkins the majority of the time, cut out dairy no milk, only black coffee, only FF yogurt and FF feta cheese ( no more LF) a few times a week, swapped sweeteners for raw sugar, swapped red wine for vodka, fresh lime and soda water and still NADA. Taken up cardio 3 x times a week just a few weeks ago, NADA.

    Prior to fasting/Paleo I was 10 weeks into the 12 week Body For Life Challenge, where you eat small meals of protein/carb 6 times a day (I managed 4 meals maybe 5 most days) and did cardio 3 x times a week and lifted heavy weights 3 x times a week with a free day once a week, eat what you like and do no exercise. This has worked well for me in the past though I was finding the exercise part increasingly harder to stay motivated. I am a post menopausal woman in my late 50’s with 20 lbs to lose when I first started fasting in February 2013 well that was then, now with the weight gain, it is more like 30 lbs. I have been mega stressed since joining FB groups where people are dropping weight and you are stagnant, it can be totally demoralising and demotivating and although it is motivational and supportive for those who lose for those who do not it can be depressing.

    I have no idea of where to go from here but tonight I went and bought some (hemp) milk to go back to having my morning cup of tea which I have missed so much. I am giving up fasting for now and will see what happens, I will try and have my first meal of the day as early as I am able, Greek yogurt with berries or an omelette with spinach or meat/fish and veggie at 3 meals a day to be swapped around at will and with a handful of nuts or 1 piece of fruit for a snack.

    Maybe IF has nothing to do with my not losing weight and maybe it is all to do with quitting smoking, I have tried so many protocols these past 6 months even including progesterone cream and iodine therapy and nothing else has worked, what harm can it do quitting fasting?

  184. I should add that when I was “off” the 5:2 fasting I was still fasting of sorts as I don’t very often eat at night, don’t eat breakfast and used to eat at about 10am, since starting 5:2 however I was stretching out my first meal until at least 12 noon most days, so in effect I have been fasting in different ways for 6 months and now weigh 10 lbs more than when I started.

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  186. I have PCOS and have been thinking of doing 5 days of water fasting every now and then to try and regulate my hormones. Now I’m dubious about what to do … Do you know of other ways to regulate hormones?

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  188. Great article!

    I also discussed this, on my blog : http://adfasting.com/2013/09/08/is-adf-better-suited-for-men-and-not-women/

    But I didn’t go into as much detail as you did. Well done!

    As a male, I’ve never been interested in “dieting” and generally just looked at extra exercise as the “solution” to weight gain.

    Ive been doing ADF for nearly 5 months now, and its been great.

    In my blog, I try to mention (as often as I can) that ADF and other forms of CR might not suit everyone, and that you should get a doctors advice before starting.

    CR / ADF is not a magic bullet, as its unsuitable for many reasons:

    – Women see less benefit

    – Athletes really need protein, so restricting protein will guarantee lower athletic ability

    – Children (like athletes) need protein for growth

    – People (eg may women) who have a hormonal balance that can susceptible to CR / ADF

    Ultimately: Your mileage may vary

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  190. Hi Stefani
    Im a danish personal trainer, sports nutritionist and scientist who wrote a reply to the “fasting for women”-critique, with basis in your post (because all the IF-skeptics refer to your post ;o). You can find it here:

    I just thought you should know, as i don’t like commenting on people behind their backs ;o)


  191. Hi, I’m Sandee, a french pro photographer and nutrition freak. i apologise in advance for any typos, still have tons to learn in english.

    Actually there’s one extremely important point that is not pointed out in this studies and in your article. What food where the people used in theses studies fed with ?! We know that hormonal response will not be the same depending on either you feed people with high carbohydrates meal or high lipidic diet. I’m hypoglycemic, trying to lose these 10 last Lbs, interested in ketogenic diet and learning about it. Seems like fasting causes similar hormonal response as for ketogenic diet (low carbohydrate, high fat intake) and done properly, it’s supposed to be very beneficial on many levels.

    Actually, most wild animals, after killing their prey, go for the fat and other spare parts, instead of rushing to the meat, as we do… That’s what got me interested in this kind of diet. As an hypoglycemic person with bad insulin responses, I seem to do much better on very low carbohydrates diets. So what if these people on these studies, fed once a day and complaining about hunger and higher cholesterol, were fed with a high carbohydrate meal ? The test results can not be either good or accurate. Hormonal response would be different with a different type of diet. And maybe IF would then be beneficial for either men and women on a high lipidic diet.

    So as we lack way too much information, it’s good to say “we don’t know shit really about IF right now” 🙂

    • Hi, Sandee P !

      You have got a very good point!

      My experience of 10 years of 10-day fasts, three times a year, taught me that THE MOST IMPORTANT THING about a fast is what you eat when you do not fast. Going back on traditional various diets makes a person like a hamster running in a wheel; brings a person to square one every time they start fasting YET AGAIN. Progress only comes if the way of eating between fasts gradually adapts to the genuine developing taste of a practicing individual.After the true fast (do not know about IF, i have never tried that) of eating nothing but water my taste sharpenes a lot and does what it is evolutionary designed to do – it leads me to eat what I truly need Reading about nutrition helps with inventiveness and imagination.

  192. HI
    Thank you for this article. I have been researching IF everywhere trying to figure out if this is mainly a male focussed beneficial idea or possible for women too.
    I have seen that you respond to Dave Asprey from BulletProof Coffee and that diet.
    I have started doing the Bulletproof coffee and food choices but am concerned that it may not be ideal.
    Firstly I cannot figure out- as a woman- if doing IF everyday the Bulletproof way is the way to go OR only doing IF every other day or a only a day or two a week?
    I have no idea. It is very confusing.
    I understnad the point to the grass fed butter and MCT oil in coffee and then not eating until 2pm’ish. However I am wary of it either messing up my system or causing me to gain weight as well as causing hormonal issues. AHHH!
    I am in my late 30s and am regular weight, but would like to be leaner. And i am moderately active.
    I drink the bulletproof coffee w grass fed ghee and MCT oil at 8am’ish. Then at 2pm’ish (12noon if I am working out that day) I drink a green protein smoothie with greens, berries and a plant based protein powder. Makes about a litre.
    Then a meal ast 7pm’ish which is grass fed beef or fish and vegetables. Once and a while i have some red wine and two to three times a week I will ahve some sweet potatoes or quinoa or say sushi if i am eating out.

    Does this sound like a healthy eating plan? Again I feel I am constantly reading about nutrtion, science of the body and avoiding high risk diet trends- but try to eat whole foods and healthy foods.
    Yet the more I read the more confused I get.

    Any thoughts or feedback?

    • As an active woman, I’d say more carbs would not do you harm, and, well, I’m not a huge fan of fasting. Nonetheless if it works for you… the only way to know is to try it. If you start exhibiting any symptoms, then you know it’s too restrictive and need to add in more food, carbs, relaxation, etc. 🙂

  193. Thanks for this in-depth discussion.
    I used to be very opposed to fasting. After all, it tells your body that it’s starving, right? So I’d always read. And that was after I took a couple of trips to Thailand for fasting/colonics vacations (I know, sounds crazy, but I did it). I decided after a bad reaction to a coffee enema on the second trip that fasting was not for me. That was day 3 or 4 of what was supposed to be a 7-day fast.

    Now, I loosely follow a form of IF with mainly just a compressed eating window, roughly noon to 8 p.m. For years I dutifully ate breakfast every morning, usually high protein, but following my natural instincts, I do feel better and find it easier to maintain my weight if I *don’t* eat it, most of the time. Sometimes I do. It’s all good.

    Bulletproof coffee or tea with IF helped me peel off about 10 pounds that needed to go this spring and summer. I still have it a couple of mornings a week, but often I don’t bother, or have bone stock with MCT oil instead. At first BPC worked so well to cut my appetite that often I didn’t eat until 2 p.m. or so. I did start to sense that I could easily slip into anorexia so I consciously avoided that. (I have never actually been anorexic.)

    I eat basically paleo/primalish, having given up grains (except for occasional white rice), and have mostly given up legumes and dairy, though I still eat Kerrygold butter and, less often, cream. I eat meat, fish, crispy nuts (soaked and dehydrated per WAPF instructions), lots of vegetables including lacto-fermented ones, some fruit, some chocolate, lots of healthy fats, especially animal fats, and occasional ice cream. I’m maintaining a comfortable weight (144 lbs, 5′ 10″), though I need to get much more serious about weight training.

    I also find it helps me to eat my carbs more at the end of the day. That helps me sleep better. The carbs I eat are *mostly* from whole foods. I’ve been in adrenal burnout before and it is not fun, but this way of eating doesn’t seem to be hurting my adrenals. I’m also putting more emphasis lately on getting to bed early.

    So from my perspective, IF can be very useful for women. I don’t know whether my age is relevant, I’m 55, very healthy, but it’s working for me at this stage in my life.

    • I think the conclusion is that doing IF in a really strict, intense way may not work as well for women in general. Doing a carb re-feed more often, not going super-low in carbs, and making sure to get plenty of rest would probably help women who want to try IF-ing. We don’t have to be rigid about these things.


  195. Your article points out a very significant problem in general when it comes to health and medicine… most studies are done on men, not women. Thank you for writing about this particular topic.

    I’ve been practicing IF for 7 months. I’m 47, 5’2” and weighed 142 pounds when I began IF. I have since decreased my body fat by 10.3%, and increased my lean muscle by almost 6 pounds. I began with 12 hours fasting (7pm-7am) and slowly increased until I got to 16 hours per day. However, at 16 hours a day, I began gaining fat and losing muscle after only a couple of weeks. Most importantly, at 16 hours a day, I DIDN”T feel well at all. I was frustrated, and didn’t have motivation. I could not sleep well; I was too hungry. Once, I dropped back to 12-14 hours a day, my fat decreased and muscle increased again. I believe IF for 12-14 hours a day certainly works for me, but not longer. Depending on my workout the previous day and/or my food intake, I can comfortably go 12-14 hours with any problems. I wait for my body to signal it’s ready to eat (when given the option to do so). I’ve always thought I had “hypoglycemia”, but I feel that my blood sugar is very well regulated now (no highs and lows). I don’t know about HDL/LDL, HA1c, etc yet–I will have a physical soon (but, these have never been abnormal). Another change I noticed with IF is I look younger–others have commented on this too–I have fewer wrinkles and my skin looks supple. What I also practice is no snacking between meals. Also, as a distance runner, I time my starchier carbs around my runs. Additionally, I have greatly increased my fat intake by adding advocates and butter or ghee (grass-fed only). Thank you again, for shedding some light IF and women.

  196. I have been doing i/f for about 4months +. I dont have a problem not eating for 16 to 18 hrs but was rather hoping to drop a few pounds.Im 55 fit & healhty, work out 4 times /week free weights & high intensity cardio stuff.Recently im finding an intolerance to sugary carbs such as rice cakes oatcakes etc and although total calories are down im putting on weight, not alot but just didnt expect this at all. Having read your article i think i may go back to eating a protein breakfast & see how i get on. Thanks for information : )

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  199. I too did IF from February till present and im now drained, tired and bloated.. I know for dure I wasnt eating enough. I ferl tired and hungry all the time and really feel like I am dealing with my own eating disorder. Calorie count is a place I joined but instead of giving me help, I feel like I get bashed for ehat im not doing right..I also lost , y period and started increasing a little. I love shredded wheat and kashi and I like to eat it for breakfast but feel so bloated after eating it.. 30 years old
    158 /5″11

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  203. Strange, but IF has actually worked so amazing for me – I’ve been doing it for a year and a half and I sleep so well, never feel stressed, etc. Maybe its because my feeding windows aren’t very small? I find I still get the effects of IF and a fasted workout on a 10/9 hour feeding window. Then again, my periods aren’t regular in the first place and I’ve never had an appetite in the morning. Funny how a simple thing can affect people in so many different ways.

  204. Dear girls, please beware, read the following.

    Studies in animals have shown that changes in diet can alter the function of genes – known as epigenetic change.
    It is a growing field trying to understand how the environment interacts with genes.
    In this study, the researchers took samples from the umbilical cord and looked for “epigenetic markers”.
    They showed that mothers with early pregnancy diets low in carbohydrates, such as sugars and starch, had children with these markers.
    They then showed a strong link between those same markers and a child’s obesity at ages six and nine.
    Professor Keith Godfrey, who is from the University of Southampton and led the international study, told the BBC: “What is surprising is that it explains a quarter of the difference in the fatness of children six to nine years later.”
    The report says the effect was “considerably greater” than that of birth weight and did not depend on how thin or fat the mother was.
    The changes were noticed in the RXRA gene. This makes a receptor for vitamin A, which is involved in the way cells process fat.
    Professor Godfrey said: “It is both a fascinating and potentially important piece of research.
    “All women who become pregnant get advice about diet, but it is not always high up the agenda of health professionals.
    “The research suggests women should follow the advice as it may have a long term influence on the baby’s health after it is born.”
    Professor Mark Hanson, of the British Heart Foundation, said: “This study provides compelling evidence that epigenetic changes, at least in part, explain the link between a poor start to life and later disease risk.
    “It strengthens the case for all women of reproductive age having greater access to nutritional, education and lifestyle support to improve the health of the next generation, and to reduce the risk of the conditions such as diabetes and heart disease, which often follow obesity.”

    Love, Lana

  205. Hi Ladies,
    I am a long term IF lady, it came as normal to me, for me, it’s always been the evening dinner as I don’t sleep well at nights with food in my stomach. Perhaps was a Buddhist monk in my past life :).
    Now as long as I remember, since a kid of 10, I have been largely non dinner person. But 10 years ago, I became very committed to yoga, and in the evening, it is my pranayama and meditation practise, hence, my last meal has to be 6 hours beforehand, which means around 2pm, the meal must finish. I loved the emptiness in the body as it helps to access deep spiritual insights.
    I eat pretty well most of my last 15years, no junk, again, I was a fitness trainer, then a yoga teacher. My weight been pretty much the same since I was 17, I weigh around 50kg on 163cm frame.
    I have always been super active and super healthy, meaning rarely get any flus or colds while others are down and out in winters or any health concerns.
    However, 4 years ago, I started having a bad case of heart palpitations out of the blue, and was diagnosed as having benign ventricular ectopic beat. It may be benign but it is a huge clam down on my overachiever lifestyle.
    My mojo is seriously downtrodden!
    In the last years I noted that it is a lot worse when I am hungry, or menstruating.
    I felt that IF could mean a woman may not get enough nutrients in, so I researched and came across your article, and am every pleased you have shared so much knowledge.
    I have started taking a little protein shake or an avocado around 5pm now, and it helps settling my anxiety which also increases when I am hungry,
    I love IF, but long term health consequence, for me, it’s 20 years IF, 10 years ago IF every day, could have contributed to my heart electrical functioning, plus my over zealous practise/training.
    I am now 48years old.
    If anyone has any offer of advice, I would be most grateful and thank you all in advance
    Take care, women, remember you are AWESOME!

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  208. Very thought-provoking article and comments as usual!
    I used IF with success when I was overweight (being muscular is not in my genes so I can be overweight with a ‘normal’ BMI) and my fat deposits had ballooned. I went from 22 BMI and BF (%) to around my current levels of 19, while increasing muscle mass. I did observe that the leaner I got, the larger my eating window needed to be, until I had to almost stop IF (which didn’t matter as I was now happy with my weight and my appearance – though there is still a bit of recalcitrant cellulite just below my buttocks!).
    I started doing 36 or 24 hour fasts at the weekend once a week or a fortnight, then moved on to daily IF, with the eating window between 10pm (when I came back from work) and midnight. I was not calorie restricting (although I was no longer eating biscuits at work, nor any bread or cheese, so was eating less calories than before) and did not experience any side effects or cravings. In particular, no difference to my periods. As my weight and body fat dropped, I started being more hungry during the day and increased the length of the feeding period, until I was only fasting from 10pm (I had moved jobs) to 2pm.
    I have now reached my target weight and have more energy so I am working out at the gym (cardio and weight lifting) 10-12 hours a week, which helps to prevent putting on weight again. During the week I have around 3 ‘big’ meals a day, although ‘breakfast’ will occur several hours after getting up, and will consist of vegs, rice and fish or vegs and meat. At the weekend, I regularly do 15 to 18 hour fasts (lunch + dinner or dinner only): I actually spend a lot of that time cooking homemade meals for the coming week!
    I have never been into eating disorders but getting enough food to eat (or any food at all) was often an issue when I was growing up, and as a young adult, so I do tend to have an irrational attitude towards food: in particular, if the pantry and the freezer aren’t well stocked, I become anxious! I went into a period when I was eating a lot of crap at work and IF enabled me to relearn to distinguish between being really hungry and just craving food because I am having a bad day!
    Thumbs up to Naomi Most for noting that rats’ lives have a different timescale than ours, and that maybe this is one of the reasons the females get so ‘freaked out’ when they cannot access food for a day, and do not derive as much benefits as the males do. I have never had a pet rat, but from my experience of rabbits, they would probably be feeding almost continuously in the wild, whereas our ancestors probably spent a lot of time hunting/fishing/gathering (women can hunt small animals or fish/collect seafood) and less time eating. I can very well imagine an ancestral ‘team leader’ snapping at any woman who selfishly attempted to nibble as she ‘gathered’ instead of saving all the food, to be shared later at the camp.
    I am going to try Sharon’s tip about fasting during my periods: I tend to eat crap during that time of the month anyway.

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  215. OK so… is IFing good or bad? its hard to understand with all of the mixed comments. im a very heathy, gym everyday kinda girl and very interested in health and fitness.I want to try this only because i usually dont eat after dinner anyways and i wouldnt mind cutting breakfast out to see if i loss extra fat on my body! i want to get lean and shed so see even more visible muscle! SOMEONE HELP

  216. I need to lose 5-10 lbs at 50 yrs old. My bf has been hovering about 22% and needs to drop a few points. Thought I would try IF since cutting carbs and high fat/protein meals didnt do it. Looks like IF may be an issue for my age and sex? Already dont sleep well since meno started. Any new studies on the effects of this on women? I have been fasting 8pm-1pm and not lost anything.

  217. Wow. Thank you for saving me from what would probably be a very negative experience. I was suspicious that all the bloggers and research results I was seeing was mainly on males – great to see some real science behind these claims.

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  219. Thankyou for this! I tried IF based on exactly the same MDA article you linked to… along with a low-carb, high fat (ketogenic) paleo diet. yes I lost a ton of weight (about 60lb in total), but I ended up with adrenal fatigue, estrogen dominance and a general hormonal shitstorm that affected my marriage, and nearly ended up with a divorce and the loss of my children!

    I am slowly rebuilding my health with the help of an ND, and attempting to rebuild the relationship with my husband and kids.

    I am convinced that very low carb/ketogenic, esp when combined with IF just does not work for women in the long-term.

    • The same happened to me, I wish someone worned me before 🙁 I was on IF and slow carb for 2 months and I was so happy, high and addicted to it, being almost anorectitc I think as I also excersied 3h a day. I felt like never better before. And then it suddenly stroke me down to the ground, I endded with adrenal fatigue and metabolism demage, I was not able to sleep and work, I had pains, rush, alergies, was dizzy even when sitting and was soo soo tired it is not possible to explain someone who didn’t go through the same. Also when I started eating reguraly again and added carbs back (because I was not able to get from bed to work unless eating like 2 chockolates) my brain got mad and I was not able stop eating, binging which led to bulimia with which I still strugle more or less 🙁 Now I am trying ketogenic diet which hepled me with all the difficulties the best so far but I don’t know if I will be the same ever again. I would like to warn all women from going too far even if it feels so good at the beginning

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  225. This is a little off subject. I think I should try eating more protein but my indigestion just won’t allow it. I tried eating a breakfast from the French Atkins diet which is low fat but my stomach hurt terribly even after just one meal. Does anyone have any suggestions?

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  228. Great article. I have tried intermittent fasting on numerous occasions with absolutely zero results. In fact it seemed to increase my appetite. I am a 50 year old woman 40 pounds overweight. Those pounds have been gained in the last 5 years. 30 of those pounds have been the last two years. I have tried everything humanly possible and my weight will not budge. Metabolically I am the most perfect specimen and my doctors practice. Low blood pressure low cholesterol hi HDL outstanding blood glucose levels. No hypothyroidism. Conclusion? Perhaps leptin resistance? Attempting the leptin reset protocol. Success is approximately 60% meaning I can follow the leptin protocol 60 percent of the time. So far I have not noticed any change they say it takes 6 to 8 weeks to reset leptin. I have also done my level best to get adequate peaceful sleep. Praying that these tactics do the trick and I can finally ditch the fat that has my joints aching and has left my body feeling ugly and bloated.

  229. Sorry I havent read all the comments, so this may have been covered.
    Interesting about Men and womens differences, but it makes sense. I wonder if any women have tried IF around there monthly cycle. Men have a full hormone cycle in 24 hours. Where ours is monthly.
    Maybe if women take into account this and did fasting on appropriate days in the momnth it would work like mens success? How on earth you figure out is another question Hormones are the bain of my life (pmdd and thyroid problems) they make me fat even with diet and excercise by the book… its not fair! Although im sure they do lots of good things for me as well ;p

    • Hey so I’ve been reading some of the comments. I’m not sure if anyone has talked about feeling the same results as men do fasting daily by fasting at a particular point in their cycle, but one person did talk about fasting on the two days of their cycle that they tend to get bad cramps, and that it more or less eliminated the cramps for them. I’m not sure if it had any other results for them though.

  230. I’m a 39 year old female with PCOS. I’ve struggled with weight and regular menstrual cycles all of my adult life. As I’ve aged, I found myself eating lower and lower amounts of calories during the day over several meals, even with the proper amounts of protein/fruits/vegies just was not doing the trick. I was dropping my calorie intake to 1000cal or less just to maintain my weight with daily 45 minute Pilates workouts. With IF I’ve now lost 45lbs of excessive weight, my menstrual cycles have returned to a normal monthly event, and my cholesterol levels are phenomenal. I did have a few days of adjustment to the new eating schedule but now I am used to it and don’t have any feelings of hunger or mental struggle. I’m not sure if it’s due to PCOS but it seems to work best for my situation. I say do what works for you individually.

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  232. The vast majority of IF subjects in ALL of Varaday’s studies at the university of Ill. over a seven year period were women. They all without exception saw the same benefits as the small number of men in the studies. The IF studies on breast cancer in the UK were All women and the benefits were identical as Varaday’s except that they focused on cancer prevention instead of just weight loss. This seems counter to what you mentioned in this article. I think you might want to review these studies to determine their application to women.

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  236. my experience with IF was when i was 15-16. i first started out eat breakfast and lunch and skipping dinner. typically around a 17 hour fast. then i started getting deeper into it and only ate breakfast and would do 22-23 hour fasts. on top of that i was playing basketball. looking back on this im just horrified by the abuse i put my body through. I was 5’5 and i got down to about 125-130. But i lost muscle. I barely lost any fat and it was all muscle and my period had stopped. i eventually stopped IF but it was hard, because i was so used to it. IF YOU ARE A WOMEN I RECOMMEND NOT FASTING OVER 16 HOUR PERIOD. my period did not come back until by ob/gyn prescribed some medication. if you havent gotten your period in over a year see a specialist.

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  239. What about the IF protocol that includes a reefed or carb back-loading day each week? It is supposed to help women to recharge their metabolic hormone levels and help with leptin as well. I would love to hear feed back from anyone who has studied this or tried it out over several months. Thanks!

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  242. So I’ve kind of been accidentally IF’ing for the past two and months or so. In this time I’ve went from rarely having headaches anymore to having them more often then not, started having migraines, my sleep went from the best its been since before I could read to at least as bad as ever and I started having acid reflux again. (To be fair a sudden decrease in activity levels as well as increase in stress levels may have at least as much to do with these problems as my accidental fasting might have).
    Over the summer I was working on long hours on a farm. On the farm we would often be working for 8+ hours (so about 9+ hours after my breakfast, which was usually a couple of eggs) before our lunch break and then my dinner would usually be another 6 or so hours later. I was eating an enormous amount of food for someone my size (5’0″ and at the beginning of this about 132′ now 114′) and as much protein and fat as I could get my hands on. I lost a net of about 20 lbs, and now weigh less then I did in forth grade, which was when I started getting more and more chubby in all the wrong places (shoulders, stomach, very little fat anywhere else). I went from size 6 jeans being kind of tight to having size 4 pants fall off without a belt. Also for the first time since I started puberty I had a little bit of a sex drive, which honestly freaks me out just a little.
    However breakfast makes me incredibly nauseous, even when I was working. So when I stopped working 12+ hour days and went back to school full time and didn’t absolutely need to eat breakfast I didn’t. (Except when I’m actually hungry in the mornings and almost always this is after eating a not very good dinner the night before.) And between the avoiding breakfast thing and my activity rate went from a hell of a lot to very little, my appetite has been very wonky. Some days I’m getting hungry and eating constantly from about 10 am to 8 or 9 pm but most days (like today) I realize its 2, 3, 4 pm or so and I haven’t eaten anything at all and may not be hungry again until 10 pm or all. More and more often I feel like I’m eating not because I’m hungry, but because I know I should eat. Other than avoiding food in the mornings when I’m nauseous, I’m not trying to fast, I’m just not hungry. However it definitely seems like it could be at least part of whatever craziness is going on in my body, especially after reading this article.
    I was wondering if anyone (Stephani especially) had ideas on how to sort of reset my appetite. Because clearly something about this isn’t working.

  243. Hi Stefi,
    While I appreciate your work on IF, I would like to offer my personal experience. I have been fasting since I’m 30. I began fasting to enhance prayer, but quickly saw the health benefits. I was suffering from awful seasonal allergies, a 3 day fast on tea, did the trick. I was cured. I fasted weekly and have done longer fasts. Last year, I did a 12 day fast with absolutely no problem, I have done 5 day fasts and presently am on a 6 day fast. Fasting 36 hours a week has always helped me stay focused on eating right and helped my weight remain stable. If I go off the fasting, I gain the weight and feel uncomfortable.

    I’m 54 now and having a hard time with menopause. A longer fast, however, seems to help the hot flashes for a while. I’ve been a vegan and am now a meat eater because I’m following the Blood Type Diet by Dr. D’Adamo. I think, the O blood type in women might be more inclined to have positive results with fasting, whereas, the other Blood Types, particularly, the A Blood type would suffer.

    Those are my thoughts, thanks for your study on women and I will be reading more of your work.
    All the best, Christine

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  258. After 6 months of intermittent fasting on a daily 19:5 schedule, I’m 36 lbs lighter and feel amazing. It’s the only way of eating that feels natural to me. I hope other women will not be discouraged from trying it. At the end of the day, statistics and studies are just that and we all have to be our own “study of one.”

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  266. It’s true that reviews, books, and information in general on IF is mostly written by men.

    But I don’t think we should draw conclusions from rat studies. Agree with you that we need more human studies.

    I have personally found that IF (anywhere from 14-20 hour daily fasts) eating feels so natural to me. I initially started it to break through a weight loss plateau, but now I realize how much more it has given me: a sense of ease about eating (not control and anxiety), a better relationship with my own hunger, and the ability to differentiate emotional vs. physical urges when it comes to food.

    I sleep like a baby, have no menstrual irregularities, and don’t feel the need to overeat during feeding times. If anything, I’m less hungry and simply eat until I’m full (something I’ve struggled with learning how to do my whole life). I also no longer suffer from gallstones or digestive issues. My skin has cleared up and my yoga practice has deepened.

    Oh, and I DID experience a “healing crisis” at the beginning: I got incredibly sick and run down, which I attribute to the autophagy process. When your body stops expending energy on digestion, it’s like your cells stop and say, “OK, what other work is there to do around here?” which then begins the process of dredging up toxins, breaking down damaged cells, and releasing them (which is why you feel like crap, get the flu, or have other symptoms).

    After that, however, I settled into feeling really stable and good.

    I eat about 85 percent clean but completely indulge my sugar cravings almost daily (not to the extreme, but enough to satisfy). My weight is stable, I feel strong, and no other adverse side effects to note.

    I start the day with coffee and a splash of almond milk, and usually break the fast around 1-3, and eat until 6 or 7.

    I also went from doing insane amounts of exercise to just HIIT or strength 2/week and walking 2-3 days for about 30 min. And I haven’t gained weight.

    There’s no substitute for personal experience. If you’re thinking of trying IF, start with a 12-14 hour fast and work your way up to see how you feel.

    I would also note that many experts in IF do say that women tend to do better on shorter fasts than men. Food for thought!

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  269. Ah! Why couldn’t I have read this at the start of the year! Annoyed with my post Christmas blow out (gasp, 3 kg!) I researched and researched and came across IF, and high fat low carb eating. I thought I’d have some fun biohacking. Already living a whole foods/ paleo lifestyle, I didn’t have to change much, apart from the macro ratios I was consuming, and including the IF. First week in of IF low carb/high fat-(no breakfast/ only bulletproof coffee) I lost 1kg. 2nd week I put on 1kg, 3rd week came another kg and the forth week I was thinking this wasn’t going the way I planned, but thought if I continued, perhaps dropping my cal consumption, I would see results. All I saw was more kgs. I did measurements too- they all increased. My sleep was terrible, I had the energy high you wrote about in the mornings, but by afternoon, particularly after my first real meal, I was feeling slow, absolutely preoccupied with food, and couldn’t control my hunger. My period was also thrown out, after finally getting it on track post merina removal, it went from a 30 day cycle out to a 40 day cycle. I also lost all my desire to exercise/move!!! Feeling horrible about myself, thinking I was doing the right thing to lose weight, especially after reading numerous blogs, articles and books that all spruke the IF high fat low carb. Looking back, I realise that they were all men, and it’s great that that way of living works for them, but it’s not for everyone, especially not all women. I was trying to survive on 50-100gm carbohydrate a day, and IF. = disaster. I’ve just purchased your ‘weightless unlocked’ book, and trying to safely remove the now 8kg I have put on since before Christmas (5kg extra thanks to my biohacking IF LCHF) . Gah! Wishing I never tried the IF/ high fat low carb lifestyle. It just did not work for me.

    • Aw, Clair! I’m so sorry about your struggle. But the good news is that the body is resilient! It can definitely recover from a couple months of fasting… heck, even mine recovered from years of starving. It’s not PERFECT, of course… but I am EXCITED for you that you at least have an answer and a plan, and can’t wait to see how it goes. 🙂

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  274. Thank you for this great article! I’ve been reading about IF on Dr. Mercola’s site for a while, and found a link here today (in someone’s comments). I so appreciate the work you’ve done delineating the research on male vs. female response (especially in women, or shall I say the dearth of such research). I’ll probably still try it, since, as you point out, personal mileage tends to vary. But now I’ll be careful to try it at a time when life is pretty stable and I’m not mucking up my personal observations by trying anything else new at the same time (except not sure when that will ever be!~).

  275. Hi Stefani,
    I have a question for you on this topic.
    I am not particularly interested in taking up IF on a regular basis. But I am interested in your opinion on a 24-hour fast once a month or once every two months. Do you think there is benefit to giving the body a break every now and then?
    I am a very active female (8-10 hours a week of triathlon training) and typically eat low carb, except for days when I have intense training sessions (long or intense or both). I will add some carbohydrates in on those days but I’d like to take up a 24-hour fast on periodic rest days based on some of the benefits that can be gained from short-term IF.
    Do you think it would be beneficial?

    • Beneficial for what? What is the “break” for? The only thing I can think of maybe this working for is immune system clean up, MAYBE, but if your body is stressed out or inflamed it probably wouldnt be much help. If you do it and it makes you feel good, great. But with how active you are, you are close to fasting pretty much all of the time anyway, so I wouldn’t personally make an effort to do that MORE, if that makes sense.

  276. No conclusions should be drawn from these studies either pro or con with regard to IF for women. None of these studies are big enough or long enough to measure anything reliably.

  277. Lots of interesting responses, hope this helps another woman like the above responses have resonated with me. I am type O blood type, I must eat hardboiled eggs first thing in the morning, or I can’t focus and I have gluten intolerance/inflammation issues. I only fast when ill and my body refuses all food, the latest during a 3 day illness with fever. When I tried restricted food hours and intermittent fasting, I did get a lightness of body and energy High, only to crash and crave carbs and sugar, so not at all a good outcome. I have low blood sugar readings, low blood pressure upon rising, PCOS with painful cysts (I only ovulate on my right ovary and I can painfully feel it when it happens) and have 4 children, several early miscarriages & need to supplement with progesterone to maintain pregnancies through the 1st trimester. My endocrinologist said I would never get pregnant! I had to change my diet and my body. Body fat – at my lowest point was 16% and very irregular but heavy 2 week long periods and anemia. I had to maintain a much higher body fat to get pregnant and sustain the pregnancies, at least 22%, and my body had to hold onto my pregnancy fat reserves or my breast milk would dry up (so no dieting while nursing.) I had to eat high protein meals of meat/quinoa/eggs/legumes in order to produce enough milk. I made it through motherhood but it was very hard work to get my body to cooperate. Entering peri-menopause and now I have to find the right balance again as my hormones shift, since I’m losing hair at my temples, getting acne again and growing chin hairs, eek!

  278. Stefani, Thanks so much! I first learned about IF as I was trying to lose the last of 60 pounds I gained in my first pregnancy– only to get pregnant again. I gained 40 pounds in my second pregnancy and was excited to begin IF (with bulletproof coffee) again after he was born (I’ve always been lean, 5’2″, 125 lbs). At first I lost a lot of weight effortlessly. But since my baby was three months old I have not lost a single pound– and he will be 1-year old tomorrow. Even on bulletproof coffee, even on TWO 72 hour fat fasts. NOT A SINGLE POUND. You an imagine how I’ve cried over this. I have 25-30 pounds left to lose! I should have lost at least 10 pounds accidentally in the last 9 months! My menstrual cycle remained regular and my sleep patterns are pretty good for a mom of 2 boys under the age of 3. Anyway, I’m scared because a low carb/high fat diet makes so much sense to me, but for the next few weeks I am going to try low fat Paleo a la your Weight Loss Unlocked book. The idea of eating in sync with my menstrual cycle appeals to me as well. But first I want to experiment with low fat Paleo. Here goes . . .

  279. I stumbled across this post soon after it was first published several years ago, and I was so pleased to read it because it chimed with my experiences and concerns.
    Occasionally, when I read an online newspaper/magazine article that encourages intermittent and/or other sorts of fasting, I will post a reader comment under it that links to this blog post by Stefani, to relay the little-mentioned point that fasting might well be a bit more complex and risky for women than it is for men, and that more studies need to be done on how adult women with various health profiles and backgrouds respond to various types of fasting.
    I did notice last year the response that Mark Sissons made to the concerns Stefani had raised (here in her post, and perhaps she also raised them in communications with him specifically – I don’t exactly recall that part) in his blog Mark’s Daily Apple, and I read many of the reader comments made by women on that blog post by him, which were quite interesting and worth checking out.
    I am not sure if Stefani has posted in the intervening years an updated overview of the research on women and fasting, but I am glad to still find this original post here, with its hundreds of thoughtful reader comments.
    I ended up coming here today via a link to this post that was on a Canadian diabetes/nephrology doctor’s website. I had not heard of the Canadian doctor before today, but I was browsing different health topics online and I happened to come across his site. I first read a number of articles there which I thought were pretty reasonable and interesting, and then I discovered a blog post which was kind of uppity/snippy about Stefani’s article here, and I thought that particular post was unnecessarily dismissive and narrow-minded. Some of the reader comments below that article talk about the “rumor” that females might respond differently biologically to fasting — but it’s not a “rumor”, and Stefani had referred to the results of several published research studies, was very careful to describe how most of the research up to that point had been done on animals, gave all sorts of caveats, described very well her concerns and questions, etc. Not to mention so many reader comments from women on this post and on Sissons’ post that describe having had poor real-world outcomes from different types fasting (as well as, of course, some posts by women who had had great results from different types of fasting).
    I wanted to leave a comment on the Canadian doctor’s site saying all that, and sticking up for the very valid possibility that some women don’t do well with fasting, so it should be properly studied and discussed with an open mind, but I’m not feeling very concise tonight, and I am not sure if Stefani has posted any updated information on this topic since 2012, etc., so in the end I haven’t written anything there. Here is that article: https://intensivedietarymanagement.com/women-and-fasting-part-10/

  280. I tried intermittent fasting last year. I was amazed that I was finally able to lose weight – I lost 15 lbs rather quickly. However I started having problems with insomnia. I finally went off this diet, gained most of the weight back and cannot get more than 4 hours of sleep at night no matter what I try. Has anyone had this experience and how did you start sleeping again. I have tried every adrenal type diet since this to try to be able to sleep again – none has helped.

  281. Interesting read, I would just say as we are all individual people need to find what works for them. I have been using IF for the last two months. My aims are to increase athletic performance and for long term health benefits. I use a 14-16 hour fast with 8-10 hour feed. I have found it great, I consume the same amount of calories just at different times. I normally fast from 8pm to 10-11am. I find this patten easiest as you go to bed fed. I can do a hard training session in the morning unfed and am getting more powerful. My energy levels are better then ever, I don’t feel hungry, I used to get hungry a lot and have energy dips, now my energy levels are more stable. I sleep the same as I always have so no issues there. Also my menstrual cycle has remained the same. This works for me, I would suggest people find what pattens work for them. Eat when you are truly hungry not just when it’s lunch time.

  282. I am a 74 year old woman so I don’t have any menstrual concerns (thank goodness THAT’s over with). I have been intermittent fasting and have had incredible results: lost 22 lbs in about 2-1/2 months. In that time frame the “feasting” was limited to just a few foods: grass-fed beef, wild caught salmon, organic eggs, avocado, coconut, coconut oil, raw nuts, raw cheese, whey protein shake and greens. I do a 16 hour fast, 8 hour feast. Not only did I loose the 22 lbs I wanted to, my cholesterol dropped 65-70 points and is now below 200 again. My brother did the same diet and lost 35 lbs, BP dropped to normal (no more BP meds), and he stopped statins. I realize this is purely anecdotal, but it worked for me. I am still doing it but have expanded my food choices: still avoiding sugar, wheat, and anything else that quickly turns to sugar. I do treat myself once a week though to dessert, or pasta, or bread. I weight train and for the first time in my life have muscle definition which I was never able to achieve before, not bulky just nicely toned.

  283. Hi Stefani, thank you for this well-researched and thorough article. I found it because I was looking for info on the Bulletproof diet and how it affects women. I have been having an amazing experience on BP, most notably that my blood sugar has finally stabilized and that has positively been affecting my sleep. Delving deeper into the research and anecdotal evidence that BP-style is a more positive experience for most women. Curious if you have any resources on BP for women that you might share, or if you can point me in the right direction? Thank you! Much love and healing your way! ~Dara in Berkeley

  284. Thanks for putting this together, I enjoyed reading this article! Perhaps an update is warranted, as quite a few studies including women (mainly from Dr Krista Varady’s lab) have come out since then, showing benefits in women.

  285. I’m glad I read this before embarking on IF as a woman, as I will now be sure to ease into it and listen to my body.

    I have a query, and this may sound like over-simplified thinking, but if I usually have breakfast at 8am, and now plan on delaying it until 12pm for IF, can this 4-hour delay have such intense negative effects on my body? 4 hours just doesn’t seem like a very long time to me! : )

  286. Just read your article.

    Well, first of all, it’s not a right idea to use findings from animal studies for human cases.
    Also, I say that intermittent fasting can be good and bad for women. It depends on body fat proportions and how long you fast. Here are two studies –

    The 1st study – Eight lean women with a BMI of 20 or less and a body fat % of 20 or less, were asked to fast for 72 hours during the midfollicular phase of their menstrual cycle. They lost almost 5 pounds and saw increased levels of cortisol, and delayed follicular development. (Alvero at el. Effects of fasting on neuroendocrine function and follicle development in lean women.J Clin Endocrinol Metab. 1998)

    The 2nd study – 12 women with 25% body fat were also asked to fast for 72 hours during the same phase as the lean women. Researchers found that follicle development was similar in all cycles and was followed by ovulation in all
    women. (Olson BR et al. 1995 Short-term fasting affects luteinizing hormone secretory dynamics but not reproductive function in normal-weight sedentary women. J Clin Endocrinol Metab. )

    So I think that the less body fat a woman has the shorter her fasts must be. We have a lot of women who fast for 24 hours once or twice a week and feel fine. We published some women stories on this page – http://www.eatstopeat.org/intermittent-fasting-for-women-what-results-you-can-expect/

  287. Fasting definitely did not work for me. I found that all my bad thought around food were coming back (restriction, low calorie, eat less to lose more weight, etc) and then i felt guilty when eating. I was recently diagnosed with Adrenal “Fatigue” , and i am not surprised about it, but its good to know what the problem is so I can focus on alleviating it. Connecting to my body, and being aware of my symptoms has helped me a lot to flow more easily when it comes to food and exercise. I recently put out an E-book about how to use our inner wisdom to heal and support our weight loss goals. Its FREE on my blog.

  288. This illustrates the problem with scientific studies. A pattern is found and a causal link is established when the cause can be due to any number of things. Then the conclusion drawn from a study of only a handful of people is applied to a very diverse and large population. I have been IF’ing for many months. Now I eat once a day and I have never felt better. I still have regular periods. The only changes with my cycle have been positive, instead of nearly hemorrhaging 7 days every month my periods are lighter and a day or two shorter. No, I am not growing any unwanted hair or becoming masculine. In fact while I have lost 50 lbs, I have retained breast tissue (and lean muscle mass) both of which I never seemed to be able to do on a typical 3 meal a day low calorie diet. I haven’t had this much energy since I was a teen. Not surprising either, because as a teen I tended to eat one large meal a day. Insomnia is less of an issue than it was before. Acne is less of an issue. More hungry? Are you kidding me? When I was eating three meals a day, I was eating more at both lunch and dinner than I am able to eat in my one meal every day. The more often I ate, the hungrier I was. Granted, it took a month or so and some diet modifications before I was able to get the constant hunger to subside. I feel so much more in tune now with my actual hunger and signs of being full. No more hypoglycemia… no more constant diarrhea…. no more acid reflux… no more craving cake ALL the time! I’m actually thirsty now – before I could hardly choke down 16 oz of water any given day. I enjoy my one meal each day so much more – it is more of a feast than a chore. I am enjoying spending my food budget on quality food, rather than quantity. I am enjoying the extra time that is freed up from not having to prepare, consume and clean up after 2 other meals and snacks every day. I could go on forever with the benefits I have seen. I was clearly sick before starting this journey and now I am well. The thought of eating more than once a day now seems like trying to swallow poison. For me, no matter how healthy the food is, the extra food in those 2 meals are too much for me. It would be foolish of me to stop IF’ing based on their conclusions… and I am sure there are more women out there like me. Common sense tells me that if our hunter/gatherer ancestors were able to live and reproduce in such scarce conditions, that our bodies are built to deal with fasting. For me, it seems that fasting is even necessary to thrive. Now if you are healthy and eating 3 meals a day, then by all means keep doing it. But if you are sick and overweight, IF might be a good thing to try.

  289. I would like to add a few other factors – and personal experience – whether a women is pre, peri or post menopausal and taking/not taking hormones, whether the pill or bioidentical or synthetic (including phytoestrogens/herbal etc.) should be considered and – the studies you mention are actually calorie restriction not fasting. Fasting is nothing but water, green tea or black coffee for a 24 hour period or longer. Also whether one is in nutritional ketosis or not also makes a difference. I do not find any sleeping issues on fasting days – sometimes we fast for up to 36 hours – rather the opposite I have better deep sleep and fall asleep easily even though I feel alert and not tired – sleep is far more a function of light – and even more so if I go to the gym (HIITs and weights) on a fast day. I am well and truly post menopausal by the way and take no hormones. I would agree that beneficial metabolic changes occur more rapidly in obese women and once you are lean perhaps not so much and maybe even blood glucose levels and blood lipid levels do not appear to be as dramatically affected as in males (my husband follows the exact same regime so we have good data to compare) however I would definitely look at Dr Jason Fung’s site for fasting to cure diabetes type 2 and to improve wellness, longevity and overall health. If you are in nutritional ketosis no-one is sure about what your blood lipid levels should be so basically don’t worry as long as your HDL is good and your LDL are more of the bigger ones. And re insulin sensitivity – that depends on your liver so even if lean or at least ‘normal’ weight – you oculd still have liver issues from sugar/alcohol/NASAIDs etc or you could have reached normal insulin homeostasis – one needs to check one’s fasting insulin and HbA1c to be really sure if true fasting is actually detrimental.
    Finally ADF – alternate day dasting where fasting means only calorie free liquids has been demonstrated to have very beneficial effects in women with breast cancer and potentially all cancers so context is very important.

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