Is Intermittent Fasting Bad For You? What A Women’s Health Expert Thinks

Every once in a while, a trendy new "wellness" term emerges — paleo, keto, and intermittent fasting populate magazine headlines, with experts arguing about their benefits and drawbacks. All that noise often makes it challenging to adopt a critical lens and understand what may be valuable for each of us personally, given the characteristics that make us unique individuals, like our sex, age, and pre-existing medical conditions.

Intermittent fasting is a dietary routine that may have advantages for the right individuals, but it could be damaging for others. And while it's been a hot topic in health and wellness for years, chatter about it is again picking up steam on social media. So, with the help of a nutritionist experienced in women's health, I delved into the impact of intermittent fasting on women.

What is intermittent fasting, and why is it popular?

If you've read wellness articles in the news in the last few years, you've probably heard about "intermittent fasting." While it seems a novel approach, people of the 21st century haven't invented anything: Intermittent fasting has been documented among different civilizations, like ancient Greece, and various religions, like Christianity and Islam.

"Intermittent fasting essentially means that you are fasting for certain periods of time," says Uta Boellinger, a Birth Association for Nutrition and Lifestyle Medicine-registered nutritionist. People can fast for shorter or longer periods, up to a week, but intermittent fasting "usually refers to not eating for certain periods of the day." The eating window can vary greatly, from a radical four-hour window to more extended ones. Boellinger explains, "The more typical is what people are referring to as this sort of between 10 and 6 o'clock, so like an eight-hour eating window."

In addition to research showing that intermittent fasting has a potential positive effect on metabolism in some people, its benefits extend to other areas too — like our digestive system, which is a delicate structure for many people (ahem, me). Boellinger states that "a certain period of fasting is normal, is what the human body was designed to do, and it will have an immediate impact on digestion," adding that she has worked on cases where it reduced bloating. The favorable effects on the digestive system may even extend to the gut microbiome, as found out by recent studies.

Finally, a less-known aspect of intermittent fasting is its potential to aid cell renewal and repair. "When we are fasting, our body puts itself in a state that is called autophagy, which means that it can recycle old cells, like break them down, recycle them, and repair other cells," Boellinger illustrates.

However, not all that glitters is gold.

What are some of the potential issues associated with intermittent fasting?

Editor’s Note: Intermittent fasting could be especially harmful to anyone with a history of or propensity for disordered eating. So, while we talk about the physical and physiological health effects of this fad, it’s also crucial to keep the mental health component in mind.

Intermittent fasting in the “fertile years”

Until 1993, medical trials weren't compelled to include women, so the effects of lifestyle interventions and medicines have been overlooked in females for centuries. This also applies to intermittent fasting.

Recent research on fish suggests that intermittent fasting could harm fertility. We know research on animals isn't necessarily a cause for concern since it is unclear if it will be replicated in humans. Still, given that women's health has only recently garnered attention, it is valuable to delve into this potential drawback.

People tend to associate fertility with wanting to have kids, but having a healthy ovulatory cycle is so much more. The menstrual cycle is the only way women make the hormones estrogen, which is higher during the follicular phase, and progesterone, which is dominant during the luteal phase. These hormones are important for overall health, including bones, brain, cardiovascular and breast health.

It turns out intermittent fasting could create an imbalance in hormonal levels, as Boellinger highlights: "For women, fasting can — in some cases — cause reduction in estrogen and progesterone." This "can interfere with periods, with menstrual health and with fertility," she adds.

This doesn't mean intermittent fasting is bad for all women, but it should be contextualized and adopted with special care. "I'm not a huge fan of doing it every day and certainly not for prolonged periods of time for most women," Boellinger admits.

Women with PCOS may be the category of women in their fertile years who could benefit from intermittent fasting the most. Recent studies show how it can improve menstrual regularity and insulin sensitivity and decrease androgen levels, which are higher than normal for women with this syndrome.

"It's harder for women with PCOS to control their blood sugar levels," Boellinger clarifies, so intermittent fasting can have its role in helping reverse insulin resistance. She advises that intermittent fasting could be an effective short-term strategy for women with PCOS, but not as a long-term solution.

Intermittent fasting during perimenopause and post-menopause

When we think of perimenopause, I think most people see hot flashes, weight gain, unpredictable periods, and other unpleasant symptoms. For most women, this phase happens from their late 30s to their raging 40s. Unfortunately, this phase, which precedes the final menstruation, could last for even 10 years — a long storm before the calm of post-menopause.

Several lifestyle-based interventions can be adopted to make this (hopefully shorter than 10 years) phase of life less turbulent, but according to Boellinger, intermittent fasting isn't one of them. Fasting could raise cortisol, which is already higher in perimenopause because of the fluctuations of estrogen and progesterone that are characteristic of this phase. This, in turn, can worsen weight gain, sleep issues, and other troublesome perimenopause symptoms.

Even if it can be chaotic, be reassured: Perimenopause will end. Twelve months after the final period, the calm of post-menopause appears. In post-menopause, Boellinger considers intermittent fasting more applicable. Post-menopausal women "are at increased risk for metabolic syndrome," and "fasting can help improve insulin sensitivity and support better blood sugar control," as well as lowering inflammation and enhancing mitochondrial function.