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Is Fasting Different For Women Than Men?

by | Apr 5, 2021 | EATING/FASTING

We’ve heard many different takes on fasting for women:

Women should never fast!

ALL women should fast!

Women should only fast if they have extra weight to lose.

But which one is true?

In this article, we explore a question often asked: how is fasting is different for women? So you can decide whether fasting is right for you or the women in your life.

History of women fasting

We know that all early humans went through regular periods of fasting and feasting, women included. In fact, fasting was a normal part of life for most men and women’s history. Only in the last two centuries has food become so abundant that we can eat around the clock.

But even in the last several centuries, where fasting has been done mostly for religious purposes (not for routine lack of food), both men and women have participated. A primary difference between males and females is that pregnant and breastfeeding women are often excluded from mandatory religious fasts because of increased nutritional needs.

Women have also been included in long-term studies on the safety of prolonged fasting – no ill effects – and many other studies on various forms of fasting.[3] This contradicts the belief that science has excluded women from fasting research generally, although more research is needed on the effects of fasting on women specifically.

A recent push for women not to fast

Despite thousands of years of women depending on fasting for their survival, there are many bloggers and speakers who’ve taken a stance against women fasting. (These are typically women who’ve had bad experiences with fasting – which plenty of men have, too.)

Just because we hear about men who can blaze through a 20-hour daily fasting window with more energy than usual doesn’t mean women can do the same, they say. Never mind us hearing the same reports from literally thousands of female YouTubers and podcasters.

The “women shouldn’t fast” crowd points to studies on mice that show how females’ reproductive capabilities diminished on an alternate-day fasting schedule, and to human studies where women had lower glucose tolerance after intermittent fasting.[1][2]

While fasting can induce irregular menses and infertility in certain people, particularly underweight/undernourished women, there have been many documented cases of women being able to successfully endure a fast without negative effects.[3]

Regarding fasting’s impact on glucose, the jury is still out. Some reviews suggest a benefit when looking specifically at the women-only studies, and other studies suggest no benefit.[4]

Until we have more long-term studies evaluating the various fasting modalities, with a focus on females at different stages of their lifespan, then it will continue to be a challenge to truly understand the risks that women may face when fasting.

What we can say right now is that, given the current evidence, fasting does not appear to pose absolute greater harm for women than men, but there are basic differences in female physiology that change the way they experience a fast. 

You should always consult your healthcare provider before attempting a dietary alteration or fasting regimen, and pregnant women are not advised to fast.

How is fasting different for women than for men

1 – Women are more sensitive to reduced calories than men

It’s true that long-term calorie restriction without enough protein can diminish fertility. That’s because procreation requires an enormous amount of nutrition in women compared to men. If a woman’s body senses scarcity, i.e. too few calories over long enough time, then her evolutionary hardwiring will prevent conception to ensure her survival.[5]

Thing is, fasting doesn’t have to involve calorie restriction; and experts such as Jason Fung even recommend against long-term calorie restriction because of the associated decrease in metabolism.[6]

The key for women is to create a pattern of fasting that doesn’t involve a chronic deficit of calories.

An easy way to do this is to build feast days (and weeks) into your fasting schedule. For instance, ‘16/8’ intermittent fasters would want to take the weekends off and occasionally skip an entire week of fasting so that their body is able to cycle between periods of fasting and non-fasting.

Also, female athletes and those with low BMI (under 18.5) may want to reconsider prolonged fasting and frequent intermittent fasting. A low body fat percentage coupled with a reduced calorie diet could contribute to amenorrhea. If you experience a missed or altered period during a fasting regimen, then you should discontinue immediately and consult your healthcare provider.

2 – Women’s cycles affect their nutritional needs and fasting ability

Depending on where she’s at in her menstrual cycle, it has been proposed by some health experts that a woman may be more or less likely to have a high-energy, health-promoting fast. Please note, women’s hormones during fasting is still poorly understood and merits further clinical studies. However, some attest that the way women feel during their fasts may depend on follicle stimulating hormone (FSH) and luteinizing hormone (LH):

  • FSH prepares a woman for ovulation; estrogen rises during the mid-follicular phase and drops shortly after ovulation
  • LH prepares a woman for conception; progesterone rises after ovulation and reaches its peak during the luteal phase

Dr. Jolene Brighten, an expert in women’s health, says that the best times to fast are near ovulation – the tail end of the follicular phase. Testosterone is at its highest at this point, which means energy will be high, and blood sugar levels will be more stable.

According to Brighten in her appearance on the Ben Greenfield Fitness Podcast, she suggests that the end of the luteal phase is the worst time for women to fast, stating this to potentially be related to insulin sensitivity. “Women will see that they need more sleep, they might have a decline in energy, and they’re having cravings,” she said – “They’re more hungry.”

All of this may contribute to a fasting failure.

Brighten cautions against starting a prolonged fast or an intermittent fast longer than 12 hours towards the middle and end of the luteal phase, which is usually within a week of a woman starting her period. Whereas men can stick to stricter intermittent fasting schedules, women should listen to their bodies and “honor their cycles”, Brighten says.

Prehistoric women occasionally had to tough out their luteal phases with forced fasts. But if you feel that fasting is too stressful for your body during this time, don’t feel like you have to be a slave to your fasting schedule.

3 – Women may be more susceptible to disordered eating

Women are historically more prone to disordered eating than men.[7] Society not only imposes more pressure on women to look perfect – remember the photoshopped model scandal? – but women may also be more susceptible to the ‘highs’ of fasting.

In an animal study conducted on rats, females who had undergone significant caloric restriction showed heightened cognition and motor activity: less food, more brainpower.[8] The study authors suggested this finding may be a reason for women’s vulnerability to anorexia, though no studies have been performed to determine this connection in humans.

Does this mean that fasting will lead to eating disorders for all or even most women? Not remotely. But healthcare providers caution against fasting when individuals have (or are at risk for) eating disorders, and also when there’s a history of mental illness.

The safest bet is to consult your healthcare professional before starting your fasting journey. And to ensure that your fasting habits remain positive and health-promoting, be sure to follow these steps:

  • be clear on what your reasons are for fasting both before and after you start fasting
  • discontinue fasting if you feel it’s becoming a compulsion
  • mix up your fasting days with feasting days
  • don’t be afraid to eat heartily when you feast – it’s good for your metabolism, health, and social life!
  • alternate your intermittent fasting schedules with weeks of normal eating patterns

Summary: Fasting for Women

While fasting isn’t right for every person, women should not be afraid of the fasting lifestyle any moreso than men.

There are a few women who shouldn’t fast for more than twelve hours at a time (such as pregnant and breastfeeding moms); more who can fast sparingly; and even more who can fast regularly. It all depends on your very personalized health considerations.

If you decide to fast, consult with your healthcare provider first. Don’t get caught up in the calorie restriction game – or at least not for the long term. Be aware of where you’re at in your menstrual cycle, never feeling pressured to fast if your body says not to. And always remind yourself of the reason you’re fasting.

As a final note, if you’re not in a position to fast, there are many other ways to achieve some of the benefits of fasting. Exercise, temporary calorie restriction, hot exposure, cold exposure, and even coffee are known to boost autophagy! [9] [10] [11] [12] [13]

Read More:

[1] Sensing the Reproductive Environment

[2] Glucose Tolerance in Response to Alternate Day Fasting

[3] Safety and Efficacy of Prolonged Fasting in Women and Men

[4] Intermittent Fasting to Reduce BMI and Glucose Metabolism

[5] Calorie Restriction in Humans

[6] Biggest Loser Study

[7] Prevalence of Eating Disorders

[8] Sex Dependent Responses to Calorie Restriction

[9] Effects of Exercise on Autophagy

[10] Effect of Fasting and Calorie Restriction on Autophagy

[11] Exposure to Heat Induces Autophagy

[12] Cold Shock as a Possible Remedy for Neurological Disease

[13] Coffee Induces Autophagy