Before You Try Intermittent Fasting as a Mom, Understand This

Everywhere you look these days, someone’s talking about intermittent fasting. And honestly, I get why. When nearly 80% of women in the U.S. are overweight or obese and obesity rates have tripled in just a few decades, everyone is searching for a solution that actually works.

Fasting promises quick results, more energy, and better health. And for a lot of people, it does deliver. But here’s the part no one talks about enough: women’s bodies are not just smaller versions of men’s bodies. Our biology is different, especially once you become a mom! The way fasting affects us can be wildly different than how it affects a man. Sometimes it’s healing and helpful. Other times it’s a total disaster.

So how do you know which it’ll be for you? That’s what we’re going to figure out in this post. I’ll walk you through when fasting can be a powerful tool vs. when it can wreck your hormones, energy, and fertility. By the end, you’ll have a much clearer answer than the generic “yes” or “no” you usually see online.

Let’s dive in.

A Quick Review Of Intermittent Fasting

At a high level, intermittent fasting involves restricting the period of time during which you can eat (known as the “eating window“) and refraining from eating during other times (known as the “fasting window“).

There are several different ways to approach intermittent fasting:

1) Time-restricted eating

This method involves a fasting window and an eating window each day. Common windows include:

• 16:8 = Fast for 16 hours, Eat for 8 hours
• 18:6 = Fast for 18 hours, Eat for 6 hours
• 20:4 = Fast for 20 hours, Eat for 4 hours

Time-restricted eating is the easiest method to follow because a significant portion of the fasting window is during sleep. For example, on a 16:8 schedule, you might fast from 6pm in the evening until 10am the next day. Then, from 10am to 6pm, you eat all your meals. So out of the 16 hours of fasting, 8 hours are spent sleeping.

2) 5/2 method

This method involves eating normally for five days and then fasting for two days. During the two days of fasting, you eat less than 25% of your daily calorie intake. For example, if you eat 2000 calories per day, then you can only eat up to 500 calories on the 2 fasting days.

This is a more intense form of fasting, and your body essentially enters starvation mode during the two fasting days.

3) Alternate-day fasting

This method involves alternating between fasting and normal eating days. On fasting days, you consume 25% of your daily caloric needs. On eating days, you eat as you normally would without restrictions. This type of fasting is very intense, as your body enters starvation mode every other day.

While there are other variations of intermittent fasting, these are the main methods to be aware of.

What Is The Point Of Fasting?

People have fasted for thousands of years. Sometimes it’s for spiritual reasons (eg. Ramadan for Muslims or certain Hindu holy days), and other times simply because food wasn’t always available on demand like it is today. These days, though, most people who try fasting are doing it for the health benefits.

I’m not going to give you a dry textbook breakdown (there are plenty of articles that do that), but here’s the gist of what’s happening under the hood when you stop eating for stretches of time.

At its core, intermittent fasting causes three changes in the body, which in turn have a range of downstream benefits:

Insulin Regulation

Every time you eat, your insulin rises to help move sugar out of your blood and into your cells. If you’re constantly eating, insulin stays elevated, and over time your cells can become resistant to it. That’s when blood sugar issues start creeping in. Fasting gives insulin a chance to come down and your cells a chance to become sensitive to it again. Better insulin sensitivity = more stable energy, easier weight loss, and lower risk for chronic diseases down the road.

Cellular Autophagy

Fasting also turns on a process called autophagy, which is basically your body’s spring cleaning system. It clears out old, damaged cells and replaces them with new, healthy ones. This is why all the longevity gurus love fasting. It supposedly helps us live longer.

Fat Utilization

When there’s no new food coming in, your body has to get it from somewhere. Instead of burning glucose from your last meal, it starts breaking down stored fat for energy. That metabolic shift is why some people find fasting amazing for fat loss.

The Risks Of Intermittent Fasting For Moms

Although there are health benefits to intermittent fasting, it also comes with risks, particularly for women. Intermittent fasting (IF) is not a free-for-all. When you do IF, you restrict your calorie intake for a certain period of time. As a result, most people end up eating less because they have less time to eat. Additionally, their body’s metabolism and hunger cues adjust for the lack of food coming in for extended periods of time, and so they begin to feel less hungry. Both of these factors combined can lead to consuming fewer essential nutrients overall.

Reducing caloric intake is a hormetic stressor on the body. This means that in the right dose, the stress triggers an adaptive response that makes the body stronger and healthier.

While stress is necessary to make the body stronger and healthier, chronic stress does the opposite. Moreover, everyone’s body has a different tolerance for stress. Perhaps the most important factor in determining how much stress a body can tolerate is biological sex.

A female’s physiology is centered around reproduction. Reproduction can only happen if there is an abundance of energy to carry out the processes of ovulation, implantation, and growing a fetus to term. This is a very energy-intensive process and the body needs a constant input of nutrients to be able to carry it out.

Fasting does the opposite of that. When a person fasts, they purposely do not give the body enough calories, which then forces the body to enter survival mode. For men, this can lead to a lot of positive physiological changes. However, women seem to react very differently if their body is chronically forced into a fasted state. The body assumes there aren’t enough resources to reproduce and begins to shut down reproductive processes.

Now, let’s take a closer look at the various ways that fasting can negatively affect mothers or mothers-to-be:

1) Hormone imbalance

When you consume fewer calories, your thyroid gland releases fewer thyroid hormones. This has been proven by studies. For instance, an older study demonstrated that fasting reduces thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4). Similarly, a study on Muslim women who fast during Ramadan showed a significant decrease in T4 levels after fasting.

Therefore, women with thyroid issues are likely to worsen their condition by fasting.

In addition to thyroid hormones, studies have shown that DHEA levels significantly decrease in women who practice intermittent fasting. DHEA is a necessary hormone that helps produce other hormones like testosterone and estrogen. Unless a woman has high DHEA levels, reducing DHEA levels is not a good idea.

2) Missed period

It is a well-known fact that calorie restriction, which is what happens during fasting, can have a negative impact on a woman’s menstrual cycle. For instance, a study conducted on 85 women during Ramadan showed that almost 25% of them had changes in their menstrual cycle due to fasting. Some women experienced much longer cycles (menorrhagia), while others experienced irregularities (oligomenorrhea).

Every woman’s body has a different capacity for stress. For some women, fasting has been proven to increase cortisol, which leads the body to enter into a sympathetic state. If this happens once in a while, that’s fine. But if fasting becomes an everyday thing, over time, this elevated stress can lead to issues like amenorrhea, where a period is completely missing. Regardless of whether a woman wants to have children or not, her period is like a monthly report card. If fasting causes irregularities or missing periods, it is definitely causing more harm than good.

3) Ovary size drops and adrenal gland size increases

Research on rats has shown that while male rats can maintain themselves quite well in a fasted state, female rats do not fare as well. They experience a drop in ovary size, an increase in adrenal gland size (which usually happens when rats are exposed to high stress), and their menstrual cycles become irregular.

As a mother, this is the last thing we want. If we want to have more children, we don’t want our ovary size to decrease. Furthermore, if our adrenals are stressed, we won’t have enough energy to take care of our children.

4) Low energy levels and mood swings

Some women may experience negative effects from fasting, such as feeling cold, constipated, having headaches, low energy, bad temper, and lack of concentration, according to a study published in the National Center for Biotechnology Information. As a mother, these symptoms can make it feel impossible to tend to our children. Taking care of children is physically and mentally demanding and requires us to have an abundance of energy. If fasting is making you feel depleted, cranky, and unable to focus, it is not worth it.

5) Glucose tolerance of fasting women worsened!

This is interesting. According to this study, glucose tolerance actually worsened for women after fasting, while it remained unchanged for men. This happened to me personally as well. When I practiced intermittent fasting, my fasted glucose levels were elevated and my blood sugar would spike after I ate my first meal of the day, leaving me feeling very tired and lethargic. However, once I started having breakfast within an hour of waking up, my blood sugar and energy levels became much more stable throughout the day.

6) Nervous system dysregulation

The nervous system has two states: Sympathetic and Parasympathetic. They have opposite roles. The sympathetic is activated during “flight-or-fight” situations and during stressful activities (such as intense exercise, fasting, etc.). The parasympathetic is more active during quiet resting periods. The goal of the sympathetic nervous system is to prepare the body for strenuous physical activity, while the goal of the parasympathetic system is to conserve and store energy and regulate basic body functions such as digestion and urination.

Both states are necessary for survival, but we don’t want to overtax the body by being in a sympathetic state for too long. This can lead to various issues, including suppression of the immune system, excessive oxidative stress, increased blood pressure, atherosclerosis, inflammation, diabetes, heart disease, kidney disease, dementia, and more.

A study conducted on women who underwent a 2-day fast showed that their nervous system shifted more into a sympathetic state. If this keeps happening with intermittent fasting — and you layer on all the other stressors of daily life — your body can get stuck in a prolonged sympathetic state, which is the opposite of what you want.

7) Increased risk for eating disorder

One study followed 496 adolescent girls over five years and found that fasting was strongly linked to developing binge eating and bulimia nervosa later on. We already know that women are more vulnerable to eating disorders than men, and fasting can sometimes be the spark that lights that fire. I’ve met plenty of women who started intermittent fasting because they believed it would make them healthier, but deep down, it was really a socially acceptable way to hide disordered eating patterns and orthorexia.

8) Poor pregnancy outcomes and milk supply

Moms should steer clear of intermittent fasting during pregnancy and in the early weeks of breastfeeding. The research here is pretty clear.

One animal study found that when female rats fasted during pregnancy, their offspring had impaired brain and organ development and gained less weight. Another large census-based study looking at Muslim populations in Uganda (about 80,000 people) and Iraq (about 250,000 people) found that exposure to Ramadan fasting during the first month of pregnancy increased the risk of mental or learning disabilities in children by 50% and psychological disabilities by 63%.

A separate large study on Indonesian women found that fasting during pregnancy was linked to smaller body size and thinness in adulthood. Low birth weight itself is a big deal because it’s directly tied to impaired cognitive function. One study showed that Muslim children who were exposed to Ramadan fasting in utero during the first trimester scored significantly lower in math, reading, and writing tests at age seven compared to those who were not exposed.

Other research on maternal rats has shown that fasting can slow fetal growth by disrupting how nutrients are transported across the placenta. And yet another study found that women who fasted during pregnancy had a higher incidence of gestational diabetes.

The bottom line here is that fasting and pregnancy do not mix well.

Breastfeeding and fasting can be tricky too. Most experts recommend avoiding fasting during the first six to eight weeks after birth while your milk supply is still being established. Your body needs extra calories during that time to produce enough milk, and fasting can make it harder to meet those needs. That can lead to low milk supply and poor weight gain for your baby. Some women do successfully use fasting to lose weight later on while breastfeeding, but it requires being extremely careful about nutrition and calorie intake to make sure milk production doesn’t suffer.

Given all of these risks, most moms really don’t need to be practicing intermittent fasting at all — unless they fall into one of the very specific categories I’ll share next.

Which Moms Might Benefit From Intermittent Fasting?

There are only a handful of moms who might truly benefit from intermittent fasting. If you fall into one of the groups below, it might be worth exploring, ideally with the guidance of a healthcare provider who understands women’s hormones and metabolism.

1) Moms with PCOS

For women with PCOS, intermittent fasting can improve a wide range of health markers. One study, for example, found positive changes in body composition (like BMI, body fat percentage, visceral fat, and muscle mass), hormone balance (including LH, FSH, total testosterone, SHBG, and free androgen index), blood sugar regulation (fasting glucose, fasting insulin, and insulin resistance), and even inflammation and liver enzymes.

Even more encouraging, about 73% of women in the study saw significant improvements in their menstrual cycles. That’s a big deal for anyone with PCOS who’s trying to restore ovulation and balance hormones naturally.

2) Moms who are overweight or obese

There’s also solid evidence that intermittent fasting can be a great tool for women who have a significant amount of weight to lose. Multiple studies (here, here, and here) have shown that fasting helps reduce body fat and improve metabolic health in this group.

3) Moms who are post-menopausal women

I know several postmenopausal women who absolutely swear by intermittent fasting. And it makes sense. Once reproduction is no longer a biological priority, the body tends to tolerate fasting more easily. Some women in this stage of life find that fasting helps them manage weight, improve body composition, and maintain steady energy levels.

Mothers who fall into the above three categories could benefit from intermittent fasting. However, it is crucial that you work with a knowledgeable healthcare provider who can help you approach intermittent fasting in a way that allows you to reap the most benefits without experiencing potential risks.

Conclusion

At the end of the day, whether intermittent fasting makes sense for you as a mom really depends on your individual situation. There are a few valid reasons to consider it, like if you’re carrying excess body fat and want to lose weight, if you’re dealing with PCOS and trying to improve metabolic and hormonal health, or if you’re postmenopausal and focused on improving your body composition.

But for most moms who are at a healthy weight, the risks outweigh the rewards. Chronic fasting will disrupt your hormones, increase stress on the body, and negatively impact your fertility, and that trade-off just isn’t worth it.

The good news is that intermittent fasting isn’t the only way to reap the benefits like better blood sugar control, autophagy, and fat loss. Exercise does all of those things too… and then some! I’d argue movement is 10x more powerful than fasting because it also helps with blood and lymph flow, bone and joint health, builds muscle, supports restful sleep, boosts your mood and energy, reduces stress, and even helps you look and feel more youthful.

So if fasting doesn’t feel right for you, that’s okay. You still have plenty of effective (and honestly, safer) ways to improve your health.

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