The Benefits and Drawbacks of Intermittent Fasting for Women

Intermittent fasting (IF) has taken the world by storm in the past few years. While popular for weight loss, restrictive diets can cause irregular or missed periods, among other health concerns.

While there is little research on the specific connection between intermittent fasting and amenorrhea (the absence of menstruation), there is evidence that low-calorie diets and long periods of fasting can negatively impact the menstrual cycle.

Intermittent fasting may work for some people, but women with certain health conditions or situations are not advised to fast. We talked to the experts about who is right for intermittent fasting and how it can be done safely.

What exactly is intermittent fasting?

During intermittent fasting, you alternate between a period of eating and a period of fasting. The fasting period length is different for everyone. For example, some people do a 12-hour fast from 7 p.m. to 7 a.m. Others might do a 24-hour fast or another method entirely.

Fasting means you are not consuming anything with calories. During a fasting period, most fasters consume only no-calorie drinks, such as water, black coffee and black tea.

The intermittent eating pattern is all about timing.

"It is not a diet; you are eating less frequently. Eating less frequently provides better hormone balance, better insulin response, blood glucose, etcera," said Cynthia Thurlow, a Virginia-based nurse practitioner and nutritionist specializing in intermittent fasting.

Several studies have shown the benefits of eating this way, including improvements in health conditions such as obesity, diabetes, cardiovascular disease, cancers and neurological disorders, according to a 2020 review published in the New England Journal of Medicine. However, the study noted, "Human trials have mainly involved relatively short-term interventions and so have not provided evidence of long-term health effects, including effects on life span."

Other benefits of intermittent fasting include reduced inflammation and oxidative stress, improved brain clarity, improved biophysical markers, reduced risk of neurocognitive disorders, reduced risk of certain types of cancers, lowered insulin markers, weight loss and changes in body composition, according to Thurlow.

"Intermittent fasting can be an effective way to lose weight, reduce inflammation and lower your risk of insulin resistance," said Sanaz Ghazal, M.D., an OB-GYN and fertility specialist at Rise Fertility in Newport Beach, California.

"If you are thinking about trying intermittent fasting, remember to start slow and give your body time to adjust to a new diet. Making gradual changes to your diet over time is usually more effective and more sustainable in the long run," Ghazal recommended.

Intermittent fasting for women

Research on the topic of IF specifically for women is limited and anecdotal reports are mixed. But one surprising benefit of intermittent fasting is increased fertility.

"For women who are trying to conceive, intermittent fasting can help optimize your natural fertility by improving your chances of ovulation," Ghazal said.

The positive effects of intermittent fasting can also play a role in fertility.

"Both weight loss and decreased insulin resistance can help improve ovulatory function for women with irregular menstrual cycles, obesity or PCOS," she explained, referring to polycystic ovary syndrome.

Despite these benefits, intermittent fasting is not for everyone. It is generally not recommended for women who are pregnant or who may become pregnant, Ghazal said.

IF is not recommended in the following situations:

• Pregnancy
• Breastfeeding
• If you are younger than 18
• If you have been hospitalized recently
• If you have a disordered relationship with food, including binge eating, anorexia or bulimia

Fasting during pregnancy is not safe because it can potentially increase the risk of nutritional or vitamin deficiencies that affect fetal development and increase your risk of pregnancy complications.

"Pregnancy is a time to focus on healthy eating and consuming adequate nutrition to support you and your growing baby, not on weight loss," Ghazal said. "Restrictive diets or prolonged periods of fasting during pregnancy can cause low blood sugar, which can cause you to feel lightheaded or faint and is associated with decreased fetal movement.

"Instead of fasting or other extreme or restrictive diets during pregnancy, focus on eating a well-balanced diet with plenty of whole foods, organic fruits and vegetables, and lean proteins," she advised.

Risks of intermittent fasting

Intermittent fasting isn't "one size fits all." Amenorrhea is a real risk for women who don't get enough calories. While intermittent fasting may not specifically cause menstrual cycle disruptions, a drop in your body mass index (BMI) can. Before starting any significant dietary change, such as fasting, it's crucial to talk to your doctor for advice.

"Intermittent fasting can have some risks...including a potential increase in the risk of nutritional or vitamin deficiencies if you are not careful or monitoring your diet appropriately," Ghazal said, adding that dehydration and headaches triggered by low blood sugar are other potential effects.

Medications and chronic illness are other factors to keep in mind when considering intermittent fasting. If someone takes medication for a chronic health condition, such as diabetes or hypertension, they should check in with their primary care physician for closer monitoring, Thurlow said.

As with any diet, it's crucial to be mindful that you are getting adequate nutritional intake. If you notice menstrual changes or other side effects of intermittent fasting, the practice may not be right for you.