The Dark Side of Intermittent Fasting: Here’s Why It Could Affect Women’s Health Differently

Intermittent fasting, a diet that limits eating to a set window of time, has gained global popularity, especially for weight loss. A new study published in Diabetes and Metabolic Syndrome: Clinical Research and Reviews suggests it may not be without risks.

The study analyzed data from more than 19,000 adults in the U.S. National Health and Nutrition Examination Survey to examine long-term health outcomes based on daily eating durations. Researchers found that participants who ate for less than eight hours a day had a 135% higher risk of cardiovascular mortality compared to those who ate within a typical 12–14-hour window.

What is intermittent fasting?

Intermittent fasting focuses on when people eat rather than what they eat. It involves alternating periods of eating and fasting. The goal is to extend the amount of time the body goes without food, during which fat cells release stored sugar for energy. Experts suggest this process may help with weight loss.

Methods of Intermittent Fasting

There are several approaches to intermittent fasting, and people can follow them daily or a few times a week. The twice-a-week method, also called 5:2, involves eating normally for five days and fasting on two days, with calorie intake limited to 500–800 calories on fasting days.

Alternate-day fasting means fasting every other day with a similar calorie limit, while eating normally on non-fasting days.

Time-restricted plans separate eating and fasting into daily cycles. The most common methods are the 16/8 method and the 14/10 method. In the 16/8 method, people fast for 16 hours and eat within an 8-hour window, such as 9 a.m. to 5 p.m. The 14/10 method allows a 14-hour fast and a 10-hour eating period. Some follow stricter versions, such as 18/6 or 20/4.

Experts say most people find time-restricted fasting easier because most fasting hours occur during sleep.

Why Is Intermittent Fasting Different for Women and Men?

Intermittent fasting may affect men and women differently. Experts suggest there are risks for women regarding reproductive health, bone health, and overall well-being.

Some forms of fasting reduce calorie intake. When the body gets too little energy, it focuses on survival, which may affect reproductive functions in women. Studies on animals indicate fasting can change hormone levels and affect menstrual cycles, fertility, pregnancy, and lactation. Male hormone levels are also affected, but their reproductive functions seem less impacted.

Women require more energy for processes like pregnancy and breastfeeding. Experts say if energy intake is too low, these functions may be negatively affected. It is not yet clear if human females are affected in the same way as animals.

Potential Risks

Experts warn that fasting may reduce bone strength and density in some cases. However, it does not appear to affect bone mineral density as much as strict calorie-restricted diets, though studies are small and more research is needed.

Other possible side effects include headaches, tiredness, constipation, and overeating during non-fasting periods. Gradual changes over several months may reduce these side effects, experts suggest.

Women Who Should Avoid Intermittent Fasting

While intermittent fasting may have benefits, some women should avoid it unless cleared by a doctor. Pregnant or breastfeeding women are advised not to follow intermittent fasting due to potential negative effects on the baby.

Women with diabetes should be cautious because fasting may increase the risk of low blood sugar. Certain medications also need to be taken with food, so long fasting periods could interfere with proper dosing.

Experts say women with existing medical conditions or a history of eating disorders should consult a doctor before starting intermittent fasting.

(Disclaimer: There was a recent report on heart risks from intermittent fasting so have included that too, however, the main topic focuses on ‘Is Intermittent Fasting For Everyone? What Indian Women Should Know.’ The original article has expert quotes and tips that has been replaced with insights from Zoe’s report on the same topic. All relevant links have been provided.)