Fasting isn’t a new phenomenon. Fasting, in many forms, including what we now call intermittent fasting, has been practiced since the beginning of time — often as part of an overarching spiritual path. What is new is the burgeoning mainstream popularity of intermittent fasting and the scientific validation of the health benefits that come along with it.
As research increasingly confirms positive effects from weight loss to improved blood sugar levels, many different fasting schedules have developed and taken hold of the popular imagination. And while none of these schools of thought claim to be the only “right” way to do intermittent fasting, they do have one thing in common: they’re one-size-fits-all solutions that treat men and women the same. But that’s a mistake.
Women and Men Are More Different Than You Know
The idea of women as delicate, fragile flowers is, on a social and even on a macro-biological level, ridiculous. But on a purely physiological level, women’s bodies are simply not the same as men’s. They’re different on the outside, they’re different on the inside, and their chemistry — and how it’s affected by external factors — is also different.
This means that women’s physiological response to intermittent fasting can be different too. And while IF may work well for some women, for others it may start a chain reaction of negative chemical and hormonal reactions with far-reaching consequences.
So — to fast or not to fast? If you’re a woman, here’s what you need to know.
Intermittent Fasting, Hormones and Women’s Health
Like it or not, mother nature has designed us so that women’s reproductive systems are intricately entwined with many other aspects of health. Women’s bodies are extremely sensitive to hormonal fluctuations, and small changes in lifestyle or environment can have an outsized effect on reproductive hormones. In addition, long-term fasting can have powerful effects on other hormones — and an imbalance in one may lead to an imbalance in others.
Intermittent fasting, for women, can create issues that simply don’t affect men — beginning with an estrogen imbalance. Estrogen is one of the major female hormones, intimately connected to both reproduction and female physical characteristics such as breasts.
An estrogen imbalance can present as…
- Lack of energy
- Weight gain (which is why women tend to gain weight more easily after menopause when estrogen levels naturally decrease)
- Lower bone density/brittle bones
- Lack of muscle tone
- Poor cardiovascular health
- Impaired blood glucose control
In addition, extreme and uncontrolled intermittent fasting can affect women’s health by disturbing cortisol (stress hormone) levels, leading to anxiety, insomnia, and sugar cravings — hello, weight gain! — thyroid hormone levels, growth hormone levels and gonadotropin-releasing hormone (GnRH). When imbalances creep into this cocktail of hormones, you can suffer symptoms from depression, anxiety and weight gain to thinning hair, dry skin and irregular or even absent menstrual periods.
How Your Fertility Can Be Affected by Fasting
GnRH and estrogen are both vital to the reproductive cycle and to fertility. GnRH is the first step in the cycle of ovulation; when your body releases GnRH, this signals your pituitary gland to secrete two substances called luteinizing hormone (LH) and follicular stimulating hormone (FSH).
This, in turn, triggers estrogen and progesterone production, all of which lead to your ovaries releasing a mature egg that can be fertilized, and to an environment that can support a pregnancy once the egg is fertilized. It’s a delicately-balanced chain reaction, and if anything upsets this balance, the result can be infertility.
What does that have to do with intermittent fasting? GnRH production appears to be easily disturbed, and fasting is one of the many environmental factors that can affect it. In a 2013 study published in the journal PLOS One, it was found that intermittent fasting disrupted the reproductive cycle of female rats after 10–15 days. LH levels dropped dramatically and estradiol (an estrogen) skyrocketed. Now, in this experiment, the rats were on a very restrictive fasting schedule — food was completely withheld every other day in a fasting technique called “alternate-day fasting.” This is a much stricter protocol than most people attempt on a long-term basis, especially if we consider the small weight of rats in comparison with a human.
On the other hand, a 2016 study published in the Journal of Mid-Life Health shows that intermittent fasting may be beneficial for those who have fertility issues due to being overweight. Women who are obese or overweight may find that the weight loss spurred by intermittent fasting leads to improved fertility.
When Fasting Is Just Another Form of Stress
You probably already know that stress is bad for your body and your health. You may also know that stress is a component of many types of chronic disease, and that chronic stress can lower your immunity and make you more susceptible to acute illnesses like colds and flu. What you may not know is the range of things that your body may perceive as stress even if your brain doesn’t register them as such.
Severe calorie restriction, a dramatic change in your eating habits (such as starting a 20:4 fasting schedule when you’re used to eating all day long), working out too hard, not taking enough recovery time — these all register as stress and cause your stress hormones to kick in. And that, in turn, can start the chemical domino effect we talked about earlier, possibly sabotaging all the effort you’ve put into integrating IF into your lifestyle and the beneficial effects you might expect to reap.
Intermittent Fasting for Women May Help You Live Longer — and Even Reduce the Effects of Aging
To be fair, it may increase longevity for men too; various studies have shown that extended fasting, intermittent fasting and prolonged moderate calorie restriction may all increase longevity and decrease the effects of aging. IF has been shown to decrease inflammation (which is a component of many chronic diseases associated with aging), reduce the risk of cardiovascular disease and improve metabolic health overall and improve cognitive function.
Intermittent fasting, for both women and men, may also help reduce the effects of aging — including staving off fine lines and wrinkles. How can that be? IF can help improve your body’s ability to defend itself against free radical damage — one of the primary factors behind aging skin.
Women’s Health: Precautions for Intermittent Fasting
When it comes to fasting and women’s health, the key is moderation. Don’t jump in at the deep end with a 24-hour fast. Don’t work out like a maniac and don’t skimp on calories during your eating window — doing so puts you at risk for amenorrhea, or having your periods stop, due to stress.
Instead, start out slowly and, depending on your body’s response, work your way up to a stricter schedule.
Here are a few simple rules for getting the most benefits from IF while avoiding some of the issues most common for women:
Eat well during your eating window.
Intermittent fasting isn’t about starving yourself. Nor is it about dramatically cutting calories. And while, of course, you shouldn’t go on a junk-food binge when you do eat — that would defeat the idea of eating well — you do need to make sure that you get all the important nutrients your body needs in during your eating window. You may naturally find yourself eating less over time, and that’s OK. Your fasting hours are for fasting, and your eating window is for eating.
Fuel yourself with big nutrient-dense meals and avoid eating overly sugary or salty food. This will make your fast easier to follow and improve your overall health.
Don’t jump into a severe fasting schedule — start with no more than 12- or 13-hour fasts instead.
Eat a late breakfast or an early dinner or skip one altogether. Fasting for a long time with no preparation can set off the chemical chain reaction we discussed earlier.
When you decide to switch to a stricter protocol, don’t do it on consecutive days. Choose two to three days per week for longer fasts, and give yourself a day or two in between to recuperate. If this works well, you can always add another day.
Keep your workout to a moderate level on longer fast days, or choose a different day for workouts.
Whatever you do, don’t engage in intense physical activity on days when you’re trying out a new fasting protocol that you haven’t adapted to yet.
Don’t fast when you’re on your period.
For all the possible pitfalls caused by our unique biology, intermittent fasting certainly can be good for women’s health. Its use as a weight-loss or weight maintenance tool is undisputed, as is its potential for improving insulin sensitivity. Fasting can also have some exclusively feminine effects on women’s health, such as improving polycystic ovary syndrome and reducing the symptoms of menopause for some women.
Do not do intermittent fasting if you:
- Have a history of eating disorders such as anorexia or bulimia.
- Are currently pregnant or who want to get pregnant in the near future. Pregnant women and those who want to conceive have different nutritional needs than those who are not, and their requirements may not be met if they’re practicing IF.
- Are currently breastfeeding. Breastfeeding requires even more energy than pregnancy and again, a fasting lifestyle may not meet these needs.
- Have a sleep disorder. If you have difficulty falling asleep, staying asleep, or waking up in the morning, your body is already dealing with abnormal stress levels. The additional physiological stress of fasting is just additional stress your body should cope with.
If none of these describe you, then intermittent fasting can be an option; just start out slowly, pay attention to your body and if you want to ratchet your fasting schedule up a notch, do so gradually. Add one hour to your 12-hour fast. Give it some time and see how you feel. If it’s working for you, you can add another hour. And another. If you feel great, you might work your way up to a standard 16:8 ratio or even more.
But if you start feeling worse, or you develop the symptoms of a hormone imbalance, it’s time to drop back down to a shorter fasting period or even stop fasting altogether.
Don’t Be Afraid of Fasting — Just Be Aware
Countless women successfully incorporate intermittent fasting into their lifestyle with no ill effects. However, it isn’t for all women, and some do report problems related above. What does that mean for you?
That all bodies are not the same, and yours may or may not do well with intermittent fasting. Most of all, it means that you should pay attention to your body and the signals it’s sending you.
But if you feel great, then go ahead and embrace the lifestyle — you’ll love it.
To learn more about how fasting affects our health please study the other chapters of our guide to intermittent fasting and health.