Is Fasting Healthy For Women?
Studies keep showing us that fasting is beneficial for cancer prevention, cardiovascular health, autoimmune diseases, neurodegenerative diseases, weight loss, anti-aging, and more. This has made fasting popular and more mainstream, however, it’s important for women to know that most studies on fasting have been conducted on men or rodents. There’s very little research on how fasting affects women.
Women are complicated to study as we are cyclical beings, with fluctuating hormones. Our monthly cycles change how we react to things physically, mentally, and emotionally. Then our hormones shift again during peri- and post-menopause.
Additionally, we're all at different stages of our health journey. Some of us are moderately healthy and are trying to optimize what we can, while others are struggling to heal from a serious health condition.
A definitive, science-backed answer to the question of whether or not women should fast isn’t currently available because the research is scattered and inconclusive, but women likely have a different response to fasting than men.
Why fasting affects women differently than men
Because of the energy and nutrients required to conceive, grow, and nurture a child, female bodies are naturally more sensitive to external stressors.
When the female body senses too much stress, whether that's from calorie restriction, infrequent meals, not enough sleep, too much exercise, or something else, reproduction is the first process that gets shut down. The last thing our bodies want to do when stressed is give energy to a growing baby.
While the exact mechanism is unclear, women seem to have a stronger response to calorie restriction or fasting due to the negative impact on gonadotropin-releasing hormone (GnRH), luteinizing hormone (LH) and estradiol, which are all required to be in balance for proper reproductive function.
Depending on a woman’s sensitivity to hormonal imbalances, disturbance of these reproductive hormones can contribute to:
Menstrual cycle irregularities
Amenorrhea (loss of menstruation)
Infertility
Hypothyroidism
General hormone imbalance symptoms (PMS, acne, poor mood, hair loss, weight issues, low libido, etc.)
Over the years I’ve worked with many women who lost their periods from intense exercise regimes combined with restrictive dieting. Even if you never plan to get pregnant or think it’s convenient to not have a period, the health of your reproductive system is still critically important to your overall well-being as a female. Your sex hormones are required for strong bones, protection against cancer, mood, energy, vitality, sex drive, skin and hair health.
How to determine if fasting is right for you
So should women fast? The answer is: it depends.
Because of the lack of quality, comprehensive studies done on fasting in females, there's no clear consensus on whether it's good or bad for women. Whether or not it's a good idea for a woman to fast should depend on a number of factors:
How old she is
How active she is
Why she is fasting
What her goals are
If she has a history of hormone issues or imbalances
If she is planning for pregnancy soon
Fasting may not be ideal for women who:
Are athletes, or very active
Are extremely lean (<18% body fat)
Have sleep disorders or poor sleep
Have low reproductive hormone levels
Have low thyroid hormone levels
Are pre-menopausal (typically under age 40)
Struggle with infertility, irregular periods, or amenorrhea
The following groups of women should definitely avoid regular extended fasting (more than 12-14 hours), and should instead focus on getting enough calories and nutrients:
Young women and teens
Women planning for pregnancy
Pregnant or breastfeeding women
Females with a history of eating disorders
Some women are already walking on a fine line of hormonal imbalance, and calorie shifts with fasting may tip them over the edge into full-blown hormone dysfunction.
If you currently practice a form of regular fasting and have experienced any of the following, you may want to consider a different approach:
Poor sleep
Low libido
Thinning hair
Acne or dry skin
Always feeling cold
Irregular heartbeat
Slow recovery or healing
Negative changes to mood
Decreased athletic performance
Binge eating or strong food cravings
Inability to lose weight or unexplained weight gain
Irregular menstrual cycles or amenorrhea
We are all bio-individuals, and until more research is done, if you choose to practice fasting as a female (especially a young female of reproductive age) then pay attention to what your body is telling you. Listen to your body. If it's telling you something, don't ignore it. You'll likely do more harm than good.
If you find fasting is a beneficial practice in your life and only experience positive results, then continue on your journey. You know yourself best. You're the only one that can truly answer the question of whether or not fasting is right for you. This article might just help you make a more educated decision.
Some women thrive on regular fasting practices, some do ok with occasional fasting as long as it's done in moderation, and for others, fasting wrecks their hormones, mood, body composition, and relationship with food.
If fasting is right for you, here’s how you can practice it safely and intelligently so you don't experience negative side effects:
How to mitigate the negative side effects of fasting
Fasting by itself is not always the problem. Issues typically arise when we stack fasting on top of other stress. This is because fasting is a hormetic stressor. It's considered to be a “good stress”, one that makes us physically stronger and more resilient, in small doses. Other natural hormetic stressors are extreme cold or heat, sunlight, exercise, and certain foods. However, it's possible to overdo it.
Too much of a “good thing” is not always good. Too much fasting, either in length or frequency, can be detrimental to our health. Especially when stacked on top of an already stressful lifestyle (work, family, finances, media, poor sleep, household responsibilities, an intense exercise or training routine, a restrictive diet, environmental stressors such as EMF exposure, blue light exposure, low-quality water, etc). At some point, the body isn't able to distinguish “good” stress from “bad” stress. It just becomes chronic stress.
Since women are more physiologically sensitive to stress, fasting can be the straw that breaks the camel's back for some females. This also means two seemingly similar women can have vastly different experiences with fasting, simply based on their current level of stress.
If there's one thing you can do to make a fasting practice less harmful and more beneficial to your health as a woman, it would be to reduce stress as much as you can.
Practice breath work or meditation, eat enough calories from nourishing foods during your feeding window, prioritize your sleep, avoid overexercising, and steer clear of toxic relationships. Give your body all the signals that you're safe, you're not starving, and everything is all good.
If you're not doing those things, fasting is probably going to be a bad idea for you.
If you’re able to get other sources of stress under control, you might be able to approach fasting more intelligently and safely, in a way that supports your body and doesn't stress it out more.
Fasting safely as a female
Healthy Pre-Menopausal Females
If you're a pre-menopausal female, your body is still making reproductive hormones during your monthly menstrual cycle. These are the hormones that seem to be extremely sensitive to external stressors. Because of these sensitive hormones, pre-menopausal women need to be a lot more careful with fasting, and pay extra attention to how their body is responding.
With that in mind, here are some guidelines and precautions for young, healthy women to consider when approaching fasting:
Get Clear On Why You're Fasting
Chances are, all the things you heard fasting could do for you may not be proven for women. Some of the most common reasons women take up a fasting practice are:
Weight loss: Research shows that fasting may not be the best weight loss approach for young, healthy women (unless you have a considerable amount of weight to lose)
Improve insulin sensitivity: Fasting may actually negatively impact glucose response in pre-menopausal women (unless you have a metabolic disorder)
Boost autophagy for longevity: This is a benefit of fasting, but it's not the only way to clear out cellular debris. Alternating cold and heat exposure, HIIT and strength training, sleep, and polyphenol-rich foods and beverages all upregulate autophagy as well (plus one study actually showed that women are more resistant to fasting-induced autophagy than men). That's not to say that fasting doesn't have benefits. It can still serve a purpose in your life, especially if you're fasting for another reason like better gut health, improving your immune system, mental acuity, or a spiritual purpose.
Here's how you can get other benefits of fasting without putting too much stress on your body:
2. Practice Shorter, Less Frequent Fasts
Doing 16-18 hour intermittent fasts 7 days a week may work for some women, but many pre-menopausal females find it can lead to hormonal issues. Instead, it seems to be safer for young women to stick to shorter, less frequent fasts. Here are some examples of how to tailor your fasts to save your hormones:
Shorter Fasts: For mental clarity, circadian rhythm alignment, maintaining reproductive health. Daily 12 Hour Intermittent Fast: This is pretty easy to do as an overnight fast, very gentle on the body, and still provides many health benefits. Simply stop eating dinner anywhere between 6-8 pm, and don't eat breakfast again until 6-8 am. This is one of the techniques I teach you about in Nourished For Life.
Less Frequent Fasts: For gut health, immune system health, detoxification, spirituality. Occasional Prolonged "Fasts": If you have greater gut and immune health aspirations, many women do ok with very occasional 3-5 day calorie-restricted "fasts", limited to 1-4 times per year. Examples of these fasts include a Fasting Mimicking Diet, an Elemental Diet, or a Caloric Liquid Fast (e.g. only calories from liquids like bone broth, smoothies, vegetable juice). By practicing shorter, less frequent fasts, you'll be reducing the stress you're putting on your body on a daily basis and avoiding the down-regulation of your reproductive hormones.
3. Avoid Exercising In A Fasted State
We hear that fasted workouts are a great way to burn fat, tone up, and lose weight. However, based on one study that compared healthy men and women, the women had better muscle adaptations to exercise in a fed state compared to the men who had better results when fasted. Another study showed that being fasted or fed during an interval training program had no difference when it came to body composition in obese women; both saw equal results. It might not even make a difference if you're fasted or not during your workouts, or worse, it could hinder your results. Some women prefer to train fasted as they feel more alert, lighter, and less bloated, and that's understandable. However, it’s important to be aware of how much stress you're putting on your body in the process. As a general rule of thumb, if you're going to exercise in a fasted state, it's best to stick to low-intensity cardio or light resistance training. A HIIT class or other more intense workouts will spike stress hormones more than other types of training.
Fasting + workouts that spike stress hormones = hormonal dysfunction.
Occasional fasted workouts probably aren't a huge deal for most healthy women. But if you're doing high-intensity workouts on top of 16-hour daily intermittent fasts for a long period of time, chances are your sex hormones aren't going to like it.
4. Avoid Doing Daily Intermittent Fasting + Calorie Restriction + Low Carb All At The Same Time
Daily extended fasting, calorie restriction, and low-carb diets can all increase cortisol (our main stress hormone), decrease thyroid hormone, and down-regulate sex hormones. When you combine these methods, you're 3x-ing your chances of cortisol dysregulation, hypothyroidism, hormonal imbalances, and all the side effects that come with them (including weight gain, which is the opposite effect that most people want this combination to have). There's really no reason to fast, restrict calories, and limit carbohydrates at the same time as a young, healthy woman without a specific medical reason.
Healthy Post-Menopausal Females
Menopause is a time when women naturally stop producing the hormones that cause them to have monthly cycles. Because of this change, they're likely going to be less sensitive to dietary shifts like fasting. Post-menopausal women may not experience as many side effects from fasting, and may see better results from it, compared to pre-menopausal women.
Here are some guidelines and precautions for healthy post-menopausal women to consider when approaching fasting:
Get Clear On Why You're Fasting
Just like pre-menopausal women, it's important to understand why you're fasting and what you want to achieve.
If you're looking for body composition benefits: You might see more benefits than young women. One study showed benefits for weight loss in obese post-menopausal females, but regular calorie restriction also provided benefits. However, if you're already spiking stress hormones in a lot of other ways, fasting probably won't help you in this category.
If you're wanting to improve metabolic efficiency: The research here is lacking for post-menopausal women. One study showed improvements in insulin sensitivity, but it was a post-menopausal mouse model study on obese rodents with metabolic issues, not on healthy women.
If you want autophagy so you can maximize healthspan: The same is true here for post-menopause as it is for pre-menopause. There are a lot of other ways to maximize autophagy, and women may be more resistant to fasting-induced autophagy than men.
2. You May Be Able To Do More Frequent, Longer Fasts
Post-menopausal women are probably going to be able to do more frequent, longer fasts than pre-menopausal women for a few reasons:
Less sensitivity to fasting and shifts in calories
Not worried about reproduction, pregnancy, or breastfeeding
More of an emphasis on healthspan and longevity benefits that longer fasting can provide
With that being said, here are a few ways post-menopausal women can approach fasting:
Shorter Feeding Windows: For mental clarity, body composition, cellular health
The Crescendo Method: This is a great way to get benefits of longer, more frequent intermittent fasting while still maintaining exercise routines and metabolic efficiency. Fast for 12-16 hours, 2-3 days a week on non-consecutive days. Ideally, fasting would fall on less active days when you aren't doing hard workouts.
Regular Extended Fast: For autophagy, longevity, detoxification, spirituality
20-24 Hour Fast Every 2 Weeks: If you're looking to increase longevity with an extended fast, you could try a 24-hour fast once every 2 weeks, preferably on rest days. For example, from Saturday dinner to Sunday dinner, with Sunday being a less active day. It's best to use this as a replacement for daily intermittent fasting, not to combine the two.
3. Fasted Exercise Or Fasting + Low-Carb Might Not Be As Much Of A Problem, But That Doesn't Mean Results Are Guaranteed
Scientifically, we don't have much to stand on in terms of how fasted exercise impacts post-menopausal women vs pre-menopausal women. Additionally, no studies exist examining the effects of low carb + fasting on this population either.
However, it does seem like post-menopausal women might get benefits from fasted aerobic cardio or by reducing carbs while fasting, or at least they don't experience as many negative side effects as their pre-menopausal counterparts. We can also assume that since female sex hormones are lower, post-menopausal women might see a similar response to men with these regimens, but we don't know for sure.
Pay attention to your body. Reduce stress in other areas of your life. Talk to other women in your age group. Be honest with yourself if your fasting/exercise/diet regimen is working for you, or if it's working against you.
4. Look Out For Signs Fasting Is Working Against You
Here are some specific things to look out for as a healthy post-menopausal female that might be a red flag your fasting is working against you:
Poor sleep
Low libido
Low energy
Binge eating
Loss of muscle tone
Increased heart rate
Resistance to weight gain or gaining weight
Negative changes to mood (depression, anxiety, moodiness)
If you experience any of these things, there's no shame in cutting back your fasting, or not doing it at all. Again, there are many other ways to improve autophagy, body composition, and be a vibrant, healthy human.
Female Athletes
The exercise volume and intensity of athletes is much higher than the average person, so athletes are already putting their bodies through a good amount of stress with training. Combining large amounts of stress with a fasting routine is a fast-track to hormonal dysfunction, especially for women.
As an athlete, what you need most is fuel, probably more than you can consume in an 8-hour feeding window. Research even suggests that when athletes eat freely and unrestricted all day, they still don't consume enough energy to adequately fuel their training.
The research doesn't support that fasting improves performance in the majority of athletes, and definitely not in women. Many female athletes who fast or calorie restrict see declines in their performance, recovery, sleep, and may even lose their menstrual cycle.
If you're a female athlete, you're likely better off focusing on high-quality fuel from nutrient-dense foods than on restricting your feeding window.
Women With Specific Health Concerns
Is fasting safe for women who are working on specific health issues?
Without getting into every specific scenario, it's hard to make recommendations here, and the science isn't conclusive.
However, fasting may be helpful for a few specific health conditions (with the support and oversight of a qualified health practitioner):
Obesity
Neurological Diseases
Autoimmune Diseases
Support with Chemotherapy
Metabolic Issues (Diabetes, PCOS, etc.)
Gut Disorders (SIBO, Candida, Crohn's, etc.)
Women with these health concerns may see more pros than cons with fasting, as it gives the body the time to rest, reset, regenerate, and heal.
Regardless, approach fasting with caution, pay attention to your body, and look out for signs that it isn't right for you at this time.
Summary
Fasting likely affects women differently than men
We are lacking quality, comprehensive studies on the topic
Most women should approach fasting with caution
Fasting can work well for some women, and for others it can be a really bad idea
If you're going to fast, be clear on why you're doing it, educate yourself on the implications, and make an effort to reduce mental/emotional/physical stress
Pay attention to how your body is reacting. Fasting should improve your quality of life, not make your health worse
I hope you found this discussion around fasting and women’s health helpful!
Now I’d love to hear from you! Have you tried fasting? What type? Did you experience any positive or negative symptoms? Share and let me know!
P.s. If you know someone who might be struggling with hormone dysfunction, share this article with them!
P.s.s. If you’re interested in learning more about hormone supportive vitamins and minerals, you can check out my free workshop here.