Marks Daily Apple
Serving up health and fitness insights (daily, of course) with a side of irreverence.
19 Jun

Dear Mark: Women and Intermittent Fasting

Many differences exist between the two sexes. We look different. We sound different. We dress differently from each other. We like different things. Different genres of movies cause men and women to cry (differently). And although society, media, and culture drive and/or inform many of our differences, some are inherent and physiologically-driven. For example, men and women have different biological equipment – both external and invisible to the naked eye – that change how we interact with and respond to our environments, our exercise, our sleep, and our eating habits. Nowhere are these gender differences more evident than in the realm of health and nutrition, and yet it seems that I’ve overlooked a big one: different sex responses to intermittent fasting.

Let’s take a look at a couple recent reader emails:

Hi Mark,

I’m a woman (28 years old) who followed your recent fasting series with great interest, gave it a shot, but had mixed results. Then I read this post, which mentioned your series and questioned the suitability of intermittent fasting for women. Is it true? Do we respond differently than men? What do you think of that post? Thanks!


Dear Mark,

Paleo for Women blog says that fasting may not be for women: that it’s more suited for male physiology. I have been fasting for three years and never experienced any missed periods/sleeplessness, etc. Moreover I got a handle on my mindless eating. Can you give your word on IF for women?

Varsha Tiwary

Thanks for writing in with your questions.

First of all, I really, really liked Stefani’s post. I should say “posts,” actually, since Stefani Ruper (who wrote the post linked in the reader question) also just did a guest post on Free the Animal, in which she discussed the treatment of women’s issues in the community at large. While I don’t agree with everything she said, both were quite well done.

Even though her articles – for lack of a better phrase – “called me out” (in a completely non-confrontational way), I was actually quite happy to read them. Heck, I was happy to read them because of it. After all, I’ve always encourage people to be critical about what they think they know about nutrition and fitness, and to be skeptical about what they read on the Internet – my articles included. The beauty of MDA is that it isn’t one-sided. I get constant feedback from readers that send me down new paths of inquiry, and it’s through this kind of crowd-sourced effort that the Primal Blueprint message grows and becomes stronger than it already is.

I also appreciated Stefani’s articles because they do highlight a blindspot – not just in my own series of posts, but in nutritional science as a whole. In the push to eliminate the confounder known as inherent endocrine gender differences, they’ve forgotten that real life is a series of confounding variables all pushing, pulling, poking, and prodding at the results we get. They’ve forgotten that while their results may represent fodder for publishing and accolade accumulation and hypothesis confirmation (or rejection), real live humans in normal living situations are not placebo-controlled. That women are not the same as men and respond differently to stimuli and stressors isn’t a “confounder”; it’s a fact deserving of further study! Because what are we ultimately trying to do here – put together nice, neat, peer-review-ready trials, or help real people living real lives?

Since I’m trying to do the latter, I happily accept constructive criticism. So should we all.

So, what did Stefani’s research find?

Fasting has different endocrine effects on male and female rats.

In male rats:

No matter the duration or degree of nutritional stress, male rat brain chemistry responds with similar changes. Nocturnal activity and cognition stay fairly stable, regardless of the intensity of the fast. If you push the fast long enough, males will get a little wonky and frantic, but overall they maintain pretty well. It’s like they’re equipped with the ability to handle nutritional stressors.

In female rats:

Any degree of nutritional stress (fasting or mere caloric restriction) causes increased wakefulness (during the day, when they normally sleep), better cognition (for finding food), hyper alertness, and more energy. In short, female rats become better at finding and acquiring food when they fast, as if their bodies aren’t as well-equipped to deal with the stress of going without food. They also become less fertile, while the males actually become hornier and more fertile (probably to account for the females’ plummeting fertility). Ovary size drops (bad for fertility), adrenal gland size increases (which in rats indicates exposure to chronic stress), and menstrual cycles begin to dysregulate in proportion to the degree of caloric restriction.

In humans, the male-female fasting literature is quite scant, but Stefani also found considerable differences beween the sexes, when data was available:

  • One study, which I’ve cited before as evidence of a benefit to fasting, found that while IF improved insulin sensitivity in male subjects, female subjects saw no such improvement. In fact, the glucose tolerance of fasting women actually worsened. Ouch.
  • Another study examined the effect of alternate day fasting on blood lipids. Women’s HDL improved and their triglycerides remained stable; men’s HDL remained stable and their triglycerides decreased. Favorable, albeit sex-specific results.
  • Later, both obese men and women dropped body fat, body weight, blood pressure, total cholesterol, LDL cholesterol, and triglyercides on a fasting regimen. These people were obese, however, and perimenopausal women were excluded from the study, so the results may not apply to leaner people or women of reproductive age.

I figured I’d look through my other recent fasting posts for data on female (preferably pre-menopausal) responses to fasting. Here’s what I found:

  • In the only heretofore extant human study on fasting and chemotherapy, seven females (including a 44-year old woman who was likely premenopausal, given when menopause usually onsets, though it wasn’t explicitly stated) and three males found that IF improved their tolerance to and recovery from chemotherapy. Takeaway: male and female (mostly middle aged, though that’s the population that generally gets cancer and undergoes chemotherapy) chemotherapy patients appear to benefit equally from IF.
  • Although both men and women displayed greater increases in VO2 max and resting muscle glycogen concentration in response to fasted cycling training, only men showed greater skeletal muscle adaptations when fasted. Women had better muscle adaptations when fed. Takeaway: fasted endurance training, then, may work better for women than fasted weight training.

As it stands right now, I’d be inclined to agree that pre-menopausal (and perhaps peri-menopausal) women are more likely to have poor – or at least different – experiences with intermittent fasting, at least as a weight loss tool. That said, it appears to be a potentially gender-neutral therapeutic tool for chemotherapy, cancer, and age-related neurodegeneration patients.

As I alluded to earlier, this is what I love about this open forum we call the Internet: the fact that if you leave something out, or overlook a key point, someone will call you out on it, most likely publicly. When that happens, you grow despite yourself. If not for Stefani’s posts, I may never have taken a closer look at the inherent differences in men’s and women’s metabolic responses to fasting. I certainly receive enough feedback from female readers for whom fasting has been helpful, so it’s good to see another side.

To sum things up – if such a thing can even be done – and answer the questions in the intro, men and women have inherent metabolic and hormonal differences, and it’s evident that these differences in part determine how we respond to a stressor like intermittent fasting. I’ve never prescribed intermittent fasting as a requisite piece of the Primal lifestyle, but rather as an adornment, a choice, a potentially therapeutic strategy that each individual must test for him or herself. Although my recent series on fasting might have thrown some people off, I want to reiterate that I am not a huge IF guy. For myself, I generally fast when it makes sense – if I’m traveling and good food isn’t available, if I’m just not hungry, stuff like that. I periodically do 16/8 or 14/10 (i.e. eating in an 8 or 10 hour window) and find it works great for me because I am fully fat-adapted. But even I don’t hold rigidly to that. It’s not for everyone. And that hasn’t changed.

So who should and shouldn’t consider fasting? Have my recommendations changed?

If you haven’t satisfied the usual IF “pre-reqs,” like being fat-adapted, getting good and sufficient sleep, minimizing or mitigating stress, and exercising well (not too much and not too little), you should not fast. The pre-reqs are absolutely crucial and non-negotiable, in my opinion, especially the fat-adaptation. In fact, I suspect that if an IF study was performed on sugar-burning women versus fat-adapted women, you’d see that the fat-burning beasts would perform better and suffer fewer (if any) maladaptations.

I would also caution against the already lean, already calorie-restricted woman jumping headfirst into IF. I mean, fasting is ultimately sending a message of scarcity to your body. That’s a powerful message that can get a powerful response from our bodies. If you’re already lean (which, depending on the degree of leanness, arguably sends a message of scarcity) and restricting calories (which definitely sends a message of scarcity), the response to fasting can be a little too powerful.

I’d also say that daily fasts, a la 16/8 or even 14/10, run the risk of becoming chronic stressors and should be approached with caution by women. Same goes for ultra-long fasts, like a 36 (or even 24) hour marathon. Most of all, though, I’d simply suggest that women interested in fasting be cautious, be self-aware, and only do so if it comes naturally. It shouldn’t be a struggle (for anyone, really). It shouldn’t stop your cycle or make it harder for you to get pregnant. It should improve your life, not make it worse. If you find that fasting has those negative effects, stop doing it. It should happen WHEN (When Hunger Ensues Naturally), if it happens at all.

I’m not going to say that women should or shouldn’t fast. I’ll just echo Stefani’s advice “to look at options, to be honest about priorities, and to listen to one’s body with awareness and love.” Frankly, everyone should be doing that, but with regards to fasting, it looks like women should probably hew a little closer to her words.

Of course, if I had to make one minor quibble with the content of Stefani’s otherwise outstanding posts, it would be her source for the number of unique visitors Mark’s Daily Apple gets each month. Nowadays, we’re actually getting closer to 1.5 million monthly uniques, not 250-300,000… but who’s counting?

That’s it for me, today. What about you? If you’re a woman who has tried fasting, or know someone who fits the description, let us all know about your experiences. I’m intensely curious to hear from as many of you as I can. Thanks for reading.

You want comments? We got comments:

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  1. I am absolutely horrified that there are 70+ studies on IF in men, and yet absolutely ZERO studies done on reproductive-aged women. How can all those scientists have completely forgotten to study women? Such an extreme gender bias is mind-boggling.

    Well, I think it’s time for action. There needs to be legislation in place that forces scientists to study equal numbers of women. If women are not represented in studies, then it’s going to flow down as poorer health for women. We can’t accept that.

    Similarly, when the media (Hi Mark!) report these kinds of findings, they need to specify that it’s not yet applicable to humans on the whole, because the studies only looked at men.

    IF is being touted as a godsend and cure-all, when we actually have no idea how it affects over 50% of the population because nobody has done the studies. And apparently, before Stefani brought it up, nobody even noticed…

    Helen wrote on July 12th, 2013
  2. The following three studies show that regular mealtimes (basically the opposite of IF-ing) improved insulin sensitivity in women. Regular mealtimes also improved postprandial glucose and lipid profiles. Having breakfast, instead of skipping it as many IFer’s do, had similar beneficial effects. In general, there were very positive results for women having small, regular mealtimes and not skipping meals.

    When you add this information to the fact that one study found IF did NOT improve insulin sensitivity in women, AND actually worsened their glucose tolerance, and you’ve got some pretty interesting evidence to be going on with. Obviously, fasting has vastly different effects on men vs women. We can’t assume that what’s good for one will be good for the other.

    These studies are small and sparse, and more research is needed, but the indication is that small regular meals, including breakfast, may possibly be better for women’s health than IF.

    Helen wrote on July 12th, 2013
  3. I do not create many responses, however after browsing a few of the comments here
    Should Women Fast? | Mark’s Daily Apple. I do have a couple of questions for you if it’s okay.
    Could it be simply me or do a few of the comments look like they
    are left by brain dead individuals? 😛 And, if you are posting on other places, I’d like to keep up with anything new you have to post. Would you make a list of all of all your social community sites like your twitter feed, Facebook page or linkedin profile?

    Corazon wrote on July 18th, 2013
  4. I am a 28 year old female and I’ve been on IF for almost a month now. I have adopted a 16/8hr schedule, according to Leangains. Sometimes I push it to 18/6 if I am very busy, but that’s really uncomfortable at the end of the fast. I make sure I eat exactly as much as I burn. I have not tried fasted training yet.
    As far as I am concerned it has benefits and some drawbacks.

    1. I am MUCH thinner and look much better
    2. Belly doesn’t bloat anymore, no matter how much I eat in one sitting
    3. My mind is much more clear, I can think better while fasting
    4. Greater output during training
    5. Energy levels don’t drop at all and my blood sugar seems to be much more stable
    6. I’ve dealt with random daily nausea for years, but that has completely vanished
    7. No more cravings for terrible food
    8. The happiness I experience when I have to eat large amounts of food really rejuvenates me psychologically. I have always hated the tiny meals of the ‘grazing’ method
    9. Food tastes INCREDIBLE
    10. So much free time during the fast, I get more things done, more quickly

    1. I still wake up hungry
    2. My BM’s have become incredibly erratic, sometimes I don’t go for days, they are smaller and sometimes come with abdominal cramps. But, no bloating.
    3. If I have a slow day I am constantly thinking about food
    4. There are days where I sleep less, on other days I sleep more

    Looking at this I seem to experience more benefits. However, waking up hungry really bums me out. Like, seriously, that’s super annoying. I haven’t done this long enough to find out if IF affects my cycle. I am very curious about that!

    I hope my info helps :)

    Layla wrote on July 20th, 2013
    • FWIK, waking up hungry is usually low blood sugar. I try to have protein before bed and NO sugar (I rarely eat sugar or sweets anymore anyway), NO high-glycemic foods.

      Sally Oh wrote on May 11th, 2015
  5. I have PCOS and have been thinking about doing some water fasting, about 5 days. I don’t want to mess up my hormones any further, but on the other hand they’re already messed up. I’m not sure how to handle the situation.

    Gry wrote on August 30th, 2013
  6. I’m a 37 yo female, martial artist, no medical conditions. Overall, lean and fit but I do still have a few extra baby pounds hanging on for dear life. With 2 young children, active lifestyle and ultra-busy schedule I think IF hasn’t worked for me because of additional stressors. My husband uses IF to great affect and does it twice per week. Usually he fasts on a regular day, but will fast on a different day if schedule/situation dictate.

    My experience, on the other hand, is completely different than his. I am a miserable wreck on IF. I am painfully hungry, have a bad attitude, low energy, wakefulness at night, painful morning and noticeable lack of strength. Although I had an initial weight loss with IF, it quickly rebounded and with a vengeance. I actually felt like my body’s response to short term IF (1 day and 2 day fasts were tried) was to add fat. I’ve had much better results by eating 5 small meals per day, “juice fasting” 1-3 of those meals every day and focusing on extra water intake. I choose a high-quality vegetable/fruit juice that packs in the vitamins on a small caloric load (usually 100-150 calories). Occasionally, I will juice fast nearly all day when my hunger is low but I never make it any longer than 16 hours without eating.

    Meg wrote on September 10th, 2013
  7. Adding my experience for anyone still reading :) (I’ve read many of your comments and appreciated them all!)

    I am a 31 year old female, 5’5, about 140 lbs, active via Crossfit (2x week) and biking to work. I am not a Primal eater, but rather follow the WAPF/Traditional Foods diet. I was on the pill for about 10 years (ugh) and went off one year ago. Menstrual cycle was very slow to come back, but started to after about 6 months. However, I decided to try the 5:2 diet seven weeks ago, just when my cycles were starting to get normal… and have not had a period since then (should have had 2 by now). My concern about this led me here, and I’m now feeling like IF certainly is not worth it for me. While I did lose about 10 lbs (which certainly wasn’t easy or fun), I do not want to put my fertility and hormones at risk. More fats for me I guess :)

    Amanda wrote on September 12th, 2013
  8. Hi Mark,

    I’m actually trying out fasting right now. I fasted on yom kippur and it didn’t go so well towards the end, which made me want to work on that. I’m doing a fast from 7am-7pm (because thats the only thing that fits my scheduale :( ) with a workout before I eat, 3 days in a row, since more holidays are coming up and this is all the time I’ve got. So far, I seem to get really hungry around 1 when I would have eaten lunch. After that I’m fine. I’m REALLY surprised at how capable I am at working out on an empty stomach!

    I really appreciate this review of this topic for women specifically. Thanks!

    Lital Bridavsky wrote on September 16th, 2013
  9. I am a woman and I have been practicing IF for most of my life without labeling it. I have never been a big breakfast eater. I would begrudgingly eat what my Mom put in front of me before school (Elementary age), and quickly started skipping breakfast most days once I reached Junior High. It just felt more natural to me. I felt less sluggish and more alert in the early AM on no food. My body naturally wants to eat somewhere between 10:00 am and 12:30 pm. I continued this pattern of eating through my adulthood even while pregnant. It never caused an issue for me. I started working out in my early 30’s, and tried to adopt the 6 small meal thing because everything I read said to do so. I felt less focused/more tired and after a bit of time eating like that would become ravenous and binge eat. Obviously I put on weight even though I was working out. I decided breakfast/6 small meals didn’t work for me, so I went back to my normal eating patterns, dropped the excess weight and focused again on building muscle. I eat once my body tells me to eat, and I normally aspire to eat my last meal at 6:00 pm although I do not stress myself out about it. This is of course just me….however if you have never been a big breakfast eater I wouldn’t recommend forcing yourself to eat it, and IF may work for you.

    Elizabeth wrote on September 17th, 2013
  10. I did intermittent fasting (16/8) for a year, and then I started to have menstrual cycle changes. I’m 45, and lo and behold, I was going into menopause! Not that I want to get pregnant, but I don’t want to be menopausal right now either! So I stopped the IF, and in 2 months, I was back to normal. I’m thin anyway, so IF is not necessarily something I “need” to do, but I’m always looking for ways to optimize my health. I’ll definitely do it again in my mid-50s because it saved time not to have breakfast and I felt fine. So I like what you wrote up here because men and women are different, and that ought to be a consideration for IF. It’s not “one size fits all.” If you want to give it a try, go for it, but if you don’t like how your body responds to it, give it up.

    Paleomama wrote on November 10th, 2013
  11. 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 never like eating later than 5pm and a light meal for that. 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. From 2pm to 8am the next day, I have nothing but water or hot teas.
    I loved the emptiness in the body as it helps to access deep spiritual insights.
    I love the expansiveness of the mind not hindered by a full heavy stomach.
    I eat pretty well since in my early 30s, especially, the 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 48- 50kg on 163cm frame.
    I have always been super active and 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 very active 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.
    We don’t always absorb all the great food that we eat…
    I came to the realisation that it is what we eat, how we eat, our state of mind whilst eating and also how the body uses and absorbs the food.
    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 on a regular basis, the last 10 years ago IF every day, could have contributed to my heart electrical functioning, plus my over zealous practise/training, given the amount of food I consumed, I was never a cardio girl, but weights and long walks.
    I am now 48years old, 49 in 2 months, no sign of menopause yet, hair still all shades of dark brown.
    If anyone has any offer of advice, I would be most grateful and thank you all in advance.
    Take care, ladies, remember you are AWESOME!

    Jacque wrote on December 21st, 2013
  12. All if the catty remarks between the little girls and the sexist remarks back and fourth both by little boys and by little girls make you all look like your still mentally stuck in high school. What a bunch of grown idiots! Grow the F up!

    My metabolism is ultra fast, I cant gain weight to save my life. Intermittent fasting caused adrenal fatigue where I was fine before adding in intermittent fasting and until I read this article I couldn’t figure out what was wrong with me.

    Betsy wrote on January 1st, 2014
  13. I wonder if the majority of problems women are experiencing are from restricting calories and not the IF itself. I think a 24 hr fast could be problematic because, say, over the course of a week it could be difficult to maintain an adequate calorie level. However, i find it hard to believe that eating in a reduced window of 8-10hrs (10 hr being recommended for women) with adequate calorie intake would be detrimental.

    IMO, women have a tendency to slip into undereating tendencies and IF could definitely exacerbate or at least facilitate this. These anecdotal stories are great and I enjoy reading them, but until we have well controlled, condensed feeding window with ADEQUATE calories studies on women we can’t truly know the effects of IF.

    andria wrote on February 19th, 2014
  14. Hi Mark,

    I recently tried IF and i did the 36 hour one. I would say throughout the day i wasn’t even hungry. I think i only felt hungry twice. And it wasn’t the STARVING hungry either. But one thing i noticed – is that the morning of the 36th hour (7am) i felt exhausted. I could barely accomplish anything. Now i’m not sure if i maybe just didn’t get a good sleep, but as far as i’m concerned – i get a sleep like that every night. I kept up on plenty of water. Just wanted to let everyone know how i felt … and if that’s natural? This is my first attempt at IF.


    Natasha wrote on March 5th, 2014
  15. I am a model,30yr old, 5’81/2″ and since I have some pressure in keeping a certain shape I thought perhaps IF would be a good way of keeping a steady weight whilst allowing for some late night “treats”. Oh boy was I wrong. I went from being 125pounds to 132 pounds in a couple of months, my metabolism seems to have slowed down and my periods went from being 6 days long to 1-2 days long. I have always been healthy,regular periods, I eat mostly paleo (although champagne,wine and occassional restaurant dessert is my weakness), I run, do power plate, yoga flow and pilates. I only eat full fat, and lots of it… It has always worked a treat. I always hovered around the 125 pound mark, give or take a couple of pounds. Then everyone raved about 5/2 so I thought to try it -I did IF a couple of times a week- I followed the book and did 36hr fasts. It worked for a little bit- I lost a couple of pounds and felt very energised, but then the trouble started. Insomnia, ravenous hunger on off days ( i never ever got hungry like that before), and shortened periods. Now, IF doesn’t make me lose weight anymore. Even if I do a 500calorie day, there is no weight loss AT ALL, and the next day , with normal calorific intake, I put on weight instead. The scales have been creeping up-eek! I understand I am still slim for my height and I am not saying I NEED to lose weight, but I do notice quite a bit of fat deposits around my mid section ( I always used to only put on weight around my hips), which makes me think something bad is happening. I am working on just going back to how I did things before – 2-3 meals a day to fullness, WHEN eating, fast for 14hrs overnight, exercise on empty stomach, eat 1 hr after exercise .Now I just want my old body/metabolism back. Do you think it can come back? HELP!

    Tanya wrote on March 5th, 2014
  16. Hi my name is Martine and I have been on IF for a little over a week now and I feel fine. I do not feel weak. My body adapted to the change. I did feel a bit scared to try it cause I have heard so many bad things can happen especially if you are a woman, but thankfully nothing happened to me. I feel great and all my friends noticed the changes. I look better cause I dropped 10lbs since I started. I am happy about that. I truly think I can make this become a lifestyle for me. I can stick to it three weeks on one week off. I exercised moderately like three times a day(yoga). I feel wonderful. At the beginning I did feel a bit nauseous though but it went away now. IF works for me.

    Martine B Cylet wrote on March 31st, 2014
  17. By the way I am 30 years old

    Martine B Cylet wrote on March 31st, 2014
  18. I know I’m late to the party on this thread, but I just had to add a bit of my experiences to it.
    I’m a woman. I’m 66. Post menopausal obviously. Two years out from chemo, radiation, and stem cell transplant therapy.
    Without realizing it I’ve been gradually shifting to something like paleo eating.
    I’ve lost 50 pounds in the past three years and wouldn’t mind dropping another 20.
    Now, to what I really want to say. The biggest mistake I ever made was to do week long fasts when I was in my twenties.
    Each time I regained more weight than I’d lost. It became harder and harder to lose weight.
    Then, around the time I entered menopause, I began gaining weight in spite of eating only a thousand calories a day and running. I also got severely depressed and lost a lot of hair.
    Blood work revealed that I had Hashimoto’s Syndrome, which is an auto-immune disease that is inheritated. My problems had nothing to do with diet.
    My point is that, just because something happens around the time of menopause, doesn’t mean it actually has anything to do with menopause. So I advise all women to get a complete check up if they are having problems.
    That said, I am using your books and site to shift even more to the paleo way of eating simply because it makes sense to me that our bodies are more in tune with a million years of development than they are to the past 10,000 years.
    Oh, and I’m also adding Mindful Eating and Breathing to my efforts, because it seems to me that paying more attention to what I’m eating, what I want to eat and when I begin to feel full is an important step as well. The breathing seems useful to slow me down and help me pay better attention to my body.

    Elizabeth J. Baldwin wrote on April 5th, 2014
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    Danner Clay wrote on May 6th, 2014
  20. I am 5’5 and currently 120 lbs. I have been doing the I.F for 5 months now. I am 34 years old and a mother of 4, my youngest being 9 months old. I started off at 139 lbs. With each child I gained about 10 lbs and at my biggest I was 150lbs. I have had no problems with I.F. it is the easiest way to lose weight for myself and for my husband. I never have been able to break 127lbs.

    Esther wrote on May 14th, 2014
  21. I am a 45 year old female nutritionist, nurse and personal trainer. I counsel people on their diets and train them as well. I have been getting many asking me about a fasting protocol for weight loss and decided to try it myself. I do not need to lose weight per se but thought I’d see what effects it may have on my body. They were all positive. I did drop my body fat percentage by 2 points, noted an increase in alertness, and was able to cut out my morning coffee. At 45 I’m not menopausal nor perimenopausal, I think my paleo style of eating and exercise has kept me physically younger than most. I think the take-home here is everyone’s biology is different whether you’re comparing women to men or women to other women. Would I prescribe it for my type II diabetics? No, like Mark said one must be a fat burner first. But for most of my other clients and patients, I would if they already had their diet under control and needed the extra boost to reach their goals.

    Sherry wrote on June 19th, 2014
  22. I am a 42 year old pre-menopausal woman who is on depo (so no cycles anyway). I have been doing daily 16/8 14/10 cycles (listening to body hunger) and I choose to eat upon waking and stop eating between 4-5pm.

    I am technically “overweight” by the scale but at 5’8″ and 205 lbs I’m a size 10/12. I also lift heavy but have not been to the gym in eight weeks.

    Frankly, the HGH gains brought me to IF. I wanted the youth, muscle mass, and cognition benefits and didn’t much care about the possible masculinization. I DO worry a bit about the glucose tolerance, but as a low carber (generally) I suspect it has less effect, since my body burns ketones.

    Thus far in 3 weeks I’ve dropped a ton of weight. 16 pounds to be exact. I sleep just fine. The big problem for me is getting in enough fat and protein in the 8-10 hour window. My macros right now are 70% fat, 25% protein, 5% non-grain non sugar carbs.

    I didn’t want to lose weight, so this is an interesting side effect. I used to be obese, and wasn’t an overeater. I knew my problem was insulin, hormones, and genetics which is why I turned to ketones and lifting. So I wonder if MY experience with IF is because of those differences in hormones.

    Laura Holst wrote on July 22nd, 2014
  23. Dear Mark,

    thank you for yet another great post. I am a 37 year old woman who is brestfeeding my youngest daughter (1,5 years old) and who has followd the Dietdoctor version of low carb for a bit more than four years. Through this I have lost about 15 kg:s of excess weight and gained many health benefits such as less sleep needed, healthier skin etc. During this process I found that I no longer feel hungry in the mornings. This made me want to test 16/8 so make it easier for me not to eat when I am not hungry. I have tried this (not too strictly) for about a month now and it seems i naturally fall into a rythm of 14/10 or sometimes 15/9. 16/8 would require some struggle. The biggest benefit is the feeling I have in the mornings. I enjoy eating when I am hungry. It seems I need a night fast of at least 12 hours in this respect.

    Rjouminna wrote on August 14th, 2014
  24. Somewhat off topic..

    …”Same goes for ultra-long fasts, like a 36 (or even 24) hour marathon. Most of all, though, I’d simply suggest that women interested in fasting be cautious, be self-aware, and only do so if it comes naturally. It shouldn’t be a struggle (for anyone, really).”…

    This line made me think of how when a woman is giving birth in most hospitals, food is denied her. If a woman is giving birth and wants to eat, let her eat! On the flip side, some women don’t get hungry during a birth, which is fine if she is allowed to listen to her body.

    My most recent birth (I hadn’t even heard of PB yet) I had steak, potatoes, and greens for dinner. The energy I got from eating food, helped me go on. Out of the three births (thus far) this one was my most Primal.

    After all, birthing is a marathon. (The soreness afterwards told me it was a major workout lol.) I need fuel to keep going!

    We now may resume our original topic of IF. (lol)


    Krimson Rose wrote on August 15th, 2014
  25. Has there been any effort, in any studies, to determine whether an individual’s long-term diet-and-exercise regime (particularly while growing up) influences their later response to IF, and whether those experiences themselves display any gender bias?

    Kirstin Darke wrote on August 26th, 2014
  26. HI

    I want to respectfully submit my experience with fasting. I am a 48 year old female about to embark on another fast and very excited to do so. I did my first fast about 15 years ago. At the time, I was exhausted, both physically and psychologically from an overload of work and personal stressors. My hair was thin and frizzy, my skin pale and for my age, I definitely looked “older”. I had a puffy abdomen and was tired all the time. I frequently had tension headaches. I was drinking a lot of coffee and alcohol. My fast at that time wasn’t planned, it just seemed I fell naturally into a pattern of eating very little. I noticed after a few days of eating very little, I felt slightly better. I began to observe the physical effects more closely. Days past and I continued to eat little but some soup, juices and maybe herbal tea. The portions were tiny. I was far from hungry. It was a bit scary, not wanting to eat and not even craving anything. I didn’t want booze, I didn’t want sweets. The longer I went, the easier and easier it got. Then I started noticing changes in my hair. You would think without all those nutrients my hair would get even worse, right? My hair dresser was always pushing vitamins on me and telling me to crank up the protein to make my hair better. Well, it was coming in lustrous and full. I had never seen hair like this before. Me, of the frizzy “hair problem” hair was suddenly getting compliments on my hair. “Your hair is gorgeous!” “I have never seen such beautiful hair before!” It was bizarre and fantastic at the same time. Also, I didn’t have to blow dry it or curl it anymore. I would air dry it and would fall into fantastic natural waves. That’s when I knew I was onto something incredible here. My weight dropped gradually to a about 119 pounds and that’s where I stayed for a long. I felt fantasic and full of energy. My mood was great. My skin glowing. This is all true, I have no books or products to sell and this isn’t even my real name. I don’t want anyone to contact me, I’m just telling you what I did. Then I slowly went back to old ways. I was back to drinking, boozing and eating junk by the next year. I don’t even know why, why I would do such a thing when I felt so fantastic, but peer pressure kicked in. Soon I had gained weight, was feeling puffy and low energy again. I was surrounded by people who didn’t support a healhty lifestyle and realized I had to get rid of the bad influences. It is not easy to maintain regular fasts when people don’t believe in it or think you’re crazy. However my change in appearance was enough for me to see the truth…that fasting has amazing healing and health benefits. Maybe some women don’t take well to it, you have to know your own body. Me? I respond very well to fasting, it lightens my mood and body and I have physical proof of its benefits every time.

    Tabitha wrote on October 1st, 2014
    • Let me just add to this, I realize you are talking about IF and not long term fasting but I belive in both forms and practice them. Obviously, long term should be far and few between and IF can be done regularly. Let me further add that at age 48 I am a size 4/6, have absolutely no health problems (minus the occasional tension headache), take no medications, take no supplements and eat a primarily plant based diet with meat, fish, eggs or poultry 2 times weekly.

      Tabitha wrote on October 1st, 2014
  27. I am a 45 yr old female and I fast once or twice a year (for 5 years) and I guess I can go about 12 – 16 days and then I am done. Fasting is wonderful. I move into ketosis and have excellent energy, (I have a greater spiritual connection to Jesus, and God answers prayer in amazing ways), I drop fat, and inflammation disappears. What’s not good?

    Lisaloo wrote on October 16th, 2014
  28. I am a 57 who has done some version of IF since I was perimenopausal at age 50. It actually had a positive affect on menstruation because it shortened the length of menses. I would menstruate for at least a week. IF cut that down to 3 – 5 days. I think that it is great and wish I had done this since birth.

    Let’s journey back to when I first began Atkins in my 40s. Once I began Atkins, I had noticed a sudden cessation to migraine headaches even though I continued experiencing the auras. Once I added IF to my regimen, The auras also stopped.

    Now, I eat one large nutrient dense low carb high fat meal a day. I don’t workout but I do pack on physical activity by walking, sprinting, burpees. And when I do these activities, it is when I am fasted. HOWEVER, I do use MCT oil during my fasting window. It is my goal to run a 5K race while fasted, when I turn 60.

    When I began fasting, I did it by eat breakfast progressively later each week. For example for 2 weeks I ate a 7:00 AM instead of 6:00. Then I began eating breakfast at 9:00 then eventually 11:00 then 12:00 noon. Eventually I made it to 2. Then I would eat whatever I wanted within a 4 hour window. Now that being said, I didn’t eat much during that window; just one large meal and a small one at the end of the window. My goal was not to reduce calories but to allow my gut to complete its work and rest in between meals. Fasting enhances the human growth hormone which also enhances testosterone as it also affects insulin so it is to not surprise that it will affect estrogen.

    Mary Titus wrote on October 23rd, 2014
  29. One important note:

    “Perimenopausal” does not mean what you think it means (mentioned in the alternate day fasting reference above). Perimenopause is a period right before a woman enters menopause, not “childbearing age.” That study in fact *included* women who weren’t in menopause and women who were. It *excluded* women who were about to enter menopause.

    This is a very important clarification!

    E Mats wrote on November 21st, 2014
  30. I’ve been practicing daily intermittent fasting for 6 months on a 19:5 schedule. I’ve lost 36 lbs and feel amazing. This is the only intervention that has enabled me to take control of my appetite. Saying that IF is detrimental for all women, is like saying there’s a diet that’s perfect for everyone. Regardless of statistics and rat studies, at the end of the day, everyone has to be their own “study of one.” I hope other women won’t be discouraged to try it and will find out for themselves.

    Mimi - The Daily Fasting Blog wrote on January 12th, 2015
  31. I do eat stop eat and have for about a year. No problems and it really works for me. But everyone is different. But I found this article regarding fertility and IFing…hoping to have a baby in the next couple of years so wanted to check out the facts…

    TJ wrote on February 6th, 2015
  32. Would love to hear someone knowledgeable’s input on this.

    I am:
    a 26 year old female
    5’9″ and in overall good health
    someone with an affinity for putting on muscle

    In the last year I adopted a paleo lifestyle and IF. I dropped 20 pounds (went from 170-150lbs). I didn’t know I could even lose this much, but I am in the best shape of my life, or so it would seem. I have a lot of muscle definition, and can also lift a lot of weight. I work out 4-5x/week for 30-60min at a time.

    However, since I lost the weight, I also stopped having a period. In addition, I am having trouble falling asleep and staying asleep at night. Other than that, I don’t have any problems, but these seem to be warning signs to me.

    I don’t want to gain weight back– I like the way I look and feel– but I also want to protect my fertility and bone density.

    Any thoughts on the matter would be appreciated!

    Thanks :)

    meghan wrote on February 11th, 2015
    • Women need some fat for hormonal purposes and to have a period. I’m not sure if we need that fat on our bodies or just need to be ingesting enough good quality fats like organic coconut oil, grass-fed lard and butter. (I’m post menopausal so can’t experiment with this.)

      You may just need to add some more fat to your diet. If your body is good at digesting fat, this won’t make you fat.

      Another idea is to look for a functional medicine practitioner and have some saliva and urine testing done to start. You can also do it on your own:

      Sally Oh wrote on May 11th, 2015
  33. The research you cited is statistically horrible.
    Sample sizes of about 10 women
    Cmon man…

    Amy wrote on March 22nd, 2015
  34. In terms of the “no other excuse” for not losing weight – I have struggled with my weight and debilitating fatigue since my early 20s until I was finally diagnosed as hypothyroid in my early 40s. I also discovered quite late in life that I was wheat intolerant. That really motivated me to eliminate wheat, though I’m not quite ready to go full primal. Further, all the caloric intake levels I was told were dead wrong because they were far too high. Maybe others of you don’t have to, but I absolutely have to count calories because I am not currently able to exercise thanks to a slew of injuries. Even walking hurts. So I’m using IM (skipping breakfast) as a way of stimulating some level of fat burning that I wouldn’t otherwise be getting.

    Women do have legit considerations with hormones causing changes to digestive processes. High levels of estrogen and progesterone can slow everything down. And menopause may cause some metabolic changes. Just my 2 cents.

    Savvy wrote on April 11th, 2015
  35. I read somewhere that study did not take into account that a lot of perimenopausal women are on birth control. That women not on birth contro had no problem with fasting and benefited just as much as men. Amyone else hear this? I have no problem fasting 16/8 5 times a week. I work nights and have my last meal at 4 on work nights nd am lax on nights off but never eat after 8. I still ovulate and get regular periods. It seems the same things that promote egg quality also could ironically stop ovulation…such as exercising and fasting. I think it is a fine line you have to do just enough but not too much…a bit of a quandary for us womem

    Jenny wrote on April 13th, 2015
  36. I realize this is an older post, but I’ve been trying to research intermittent fasting for women and still not much there…so I’d like to put forth my experience. I’m in my early 60’s and started IF a couple years ago. It’s been great! I never had a weight problem til my mid-40’s when I did a career change that was more desk oriented. Gained 40+ lbs. Lost it on WW online and then gained back 10-15 lb over the course of 15+ years. I wasn’t into doing portion control, and had heard of IF. I started with the 5:2 for several months and after losing my weight, moved on to the 8 hr eating window. I don’t fast on weekends as it’s a family time and we enjoy our meals together.
    As I think on it, I believe I was doing IF all my early years, tho’ with a 12 hr eating window most days. I had a job where I had to be at work at 6 a.m. , so breakfast wasn’t generally eating. And often we didn’t always get lunch… (i worked in a hospital medical lab).
    I had a physical a few weeks back and my labs were all great… My BP normal and I’m on no meds. My HDL is >100, so that does put my total cholesterol up there, but dr said that was great as my ratios were awesome.
    I try and eat 4-6 fruits/veggies day and eat mostly whole, minimally processed foods along with exercising and minimal weight lifting.
    All in all I feel the IF has helped control my mindless eating (which isn’t good even with a healthy diet) and I appreciate my food more.
    I’ve probably rambled on enough, but thanks for letting me do so :-)

    Lee wrote on April 25th, 2015
    • Thank you for that. I’m 59 and post menopausal as well. I’ve been doing IF in 8-10 hour windows for the past few months and no ill-effects. The best thing I’d ever done for my night-time silent reflux is not eat 4 hours before bed — that’s what accidentally got me started on IF.

      Until there’s a substantial study, I’m ignoring the warnings about women and IF. There are too many variables unaccounted for to rely on them.

      Terrible sentence. Need more coffee…

      Actually, that’s my question and why I’m searching IF today: I thought fats during the fast (butter and/or coconut oil in my coffee) do not break the fast. But I can’t find any info on that.

      Leangains Martin says sugar-free sweetener and a dash of milk won’t break it (and of course a dose of BCAAs if you are fasting-training but I’m not).

      What’s the scoop with fats during fasting? Does it break the fast or not? Thank you!

      Sally Oh wrote on May 11th, 2015
  37. No conclusions should be drawn from those studies either pro or con with regard to IF for women. None of the studies are big enough or long enough to measure anything reliably.

    Sally Oh wrote on May 11th, 2015
  38. Hello all, I am new to this blog but I wanted to add something that has happened to me whilst doing the IF thingymagig!! I am 52 and I suppose i am post menopausal seeing as I havent had a period for a year or just over……until today!!! Well…..I was very surprised and remember reading something about hormonal imbalances whilst doing the IF…. Its not full on but I have had to go buy stuff that I havent had to for a year!
    As for the IF….I LOVE IT…i feel better already and it has only been nearly two weeks..I feel more awake and still sleep at night… body has stoped aching so much and mood wise I feel so much more balanced….
    Please dont tell me I have to stop it….I tried fasting on Mondays and Thursdays before but found myself getting very moody those days and not losing any weight at all…this way I eat after 11 and stop at 7 …easy and if I want chocolate i eat it….but I find I dont want to binge at all..,unlike when I was doing the two fasting days… thios has worked for me apart from the period thingy!! I will keep an eye on it and hope that it balances out again and yes i will visit the docs to check to make sure everything else is ok..I just wanted to say IT WORKS FOR ME……hopefully I dont have to stop because of this period thing……really dont want them back…I mean it is the only thing about menopause that is a great thing for me,….

    Julie Baldwin wrote on May 16th, 2015
  39. I am a guy who stubbornly resisted fasting for 5 1/5 years because I was getting pretty good results. After starting mostly eating in a mostly 11 am to 6:30 pm window, I am getting fabulous results. Fat melting off and twice as much energy. I think IF is essential for guys (after becoming fat adapted, which is also essential.) That’s how we hunter Groks evolved.

    But it is wonderful to see some thought about how women differ. Too little of that in medical research.

    Tung nguyen wrote on May 24th, 2015
  40. For what it’s worth, I am a Muslim, and I never found the fasting of Ramadan to be detrimental to my health in any way. Keep in mind that I elected not to fast when I knew that I was pregnant or breastfeeding before introducing solids. In fact, I have found that it actually brings ON my period if I was previously in a state of post-first-year breastfeeding amenorrhea. Both times that I have fasted Ramadan after having been breastfeeding for a year with absolutely no menstruation, my period came back within a week. As a Muslim, I believe that the commands of God are inherently good for me, and the Islamic rituals have been confirmed to be very health-giving practices over and over again. For this reason, I would also add that I wouldn’t recommend fasting DURING your period because it is forbidden in Islam, and I trust that it is so for a good reason. One possible side effect could be that it would disrupt your cycle. That may be where women are running into problems with IF, either fasting for too long or trying to do it while menstruating. Also, breaking the fast with dates may be helpful as well. I believe I’ve read before that dates contain some bioidentical hormones that make them helpful during childbirth.

    Annonymous wrote on June 25th, 2015

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