Unlike most diets that tell you what to eat, intermittent fasting focuses on when to eat by incorporating regular short-term fasts into your routine.
Intermittent fasting has become increasingly popular in recent years. This method may help you consume fewer calories, lose weight, and lower your risk of diabetes and heart disease.
However, a number of studies have suggested that intermittent fasting may not be as beneficial for women as it is for men. For this reason, women may need to follow a modified approach.
What is intermittent fasting?
Intermittent fasting describes an eating pattern that cycles between periods of abstaining and eating.
The most common methods include fasting on alternate days, daily 16-hour fasts, or fasting for 24 hours twice a week. For the purpose of this article, the term intermittent fasting will be used to describe all regimens.
Unlike most diets, intermittent fasting does not involve tracking calories or macronutrients. In fact, there are no requirements about what foods to eat or avoid, making it more of a lifestyle than a diet.
Many people use intermittent fasting to lose weight as it is a simple, convenient, and effective way to eat less and reduce body fat.
It may also help reduce the risk of heart disease and diabetes and preserve muscle mass.
Intermittent fasting may affect men and women differently
There is some evidence that intermittent fasting may not be as beneficial for some women as it is for men.
One 2005 study showed that blood sugar control actually worsened in women after three weeks of intermittent fasting, which was not the case in men.
There are also many anecdotal stories of women who have experienced changes to their menstrual cycles after starting intermittent fasting.
Such shifts occur because female bodies are extremely sensitive to calorie restriction.
When calorie intake is low — such as from fasting for too long or too frequently — a small part of the brain called the hypothalamus is affected.
This can disrupt the secretion of gonadotropin-releasing hormone (GnRH), a hormone that helps release two reproductive hormones: luteinizing hormone (LH) and follicle-stimulating hormone (FSH).
When these hormones cannot communicate with the ovaries, you run the risk of irregular periods, infertility, poor bone health, and other health effects.
A small 2021 study looked at 18 women ages 18–31 with PCOS over a 6-week period. Participants experienced a significant improvement in menstrual cycle regularity and reduced body fat, among other positive effects.
For these reasons, women should consider a modified approach to intermittent fasting, such as shorter fasting periods and fewer fasting days.
Health benefits of intermittent fasting for women
Intermittent fasting not only benefits your waistline but may also lower your risk of developing a number of chronic diseases.
Heart health
Heart disease is the leading cause of death worldwide.
High blood pressure, high LDL cholesterol, and high triglyceride concentrations are some of the leading risk factors for the development of heart disease.
One 2009 study of 16 obese men and women showed intermittent fasting lowered blood pressure by 6% in just eight weeks.
The same study also found that intermittent fasting lowered LDL cholesterol by 25% and triglycerides by 32%.
Higher-quality studies with more robust methods are needed before researchers can fully understand the effects of intermittent fasting on heart health.
Diabetes
Intermittent fasting may also effectively help manage and reduce your risk of developing diabetes.
Like continuous calorie restriction, intermittent fasting appears to reduce some of the risk factors for diabetes. It does so mainly by lowering insulin levels and reducing insulin resistance.
In a 2011 randomized controlled study of over 100 overweight or obese women, six months of intermittent fasting reduced insulin levels by 29% and insulin resistance by 19%. Blood sugar levels remained the same.
However, intermittent fasting may not be as beneficial for women as it is for men regarding blood sugar.
Weight loss
Intermittent fasting can be a simple and effective way to lose weight when done properly, as regular short-term fasts can help you consume fewer calories and shed pounds.
A number of studies suggest that intermittent fasting is as effective as traditional calorie-restricted diets for short-term weight loss.
A 2018 review of studies in overweight adults found intermittent fasting led to an average weight loss of 15 lbs (6.8 kg) over the course of 3–12 months.
A 2014 review showed intermittent fasting reduced body weight by 3–8% in overweight or obese adults over a period of 3–24 weeks. The review also found that participants reduced their waist circumference by 3–7% over the same period.
It should be noted that the long-term effects of intermittent fasting on weight loss for women remain to be seen.
In the short term, intermittent fasting seems to aid in weight loss. However, the amount you lose will likely depend on how many calories you consume during non-fasting periods and how long you adhere to the lifestyle.
Portion control
Switching to intermittent fasting may naturally help you eat less.
One study found that young men ate 650 fewer calories daily when their food intake was restricted to a four-hour window.
Other health benefits
A number of human and animal studies suggest that intermittent fasting may also yield other health benefits.
- Reduced inflammation: Some studies show that intermittent fasting can reduce key markers of inflammation. Chronic inflammation can lead to weight gain and various health problems.
- Increased longevity: Intermittent fasting has been shown to extend lifespan in rats and mice. The effects on longevity in humans are yet to be determined.
- Preserve muscle mass: Intermittent fasting appears to be more effective at retaining muscle mass compared to continuous calorie restriction. Higher muscle mass helps you burn more calories, even at rest.
Specifically, the health benefits of intermittent fasting for women must be studied more extensively in well-designed human studies before any conclusions can be drawn.
Best types of intermittent fasting for women
When it comes to dieting, there is no one-size-fits-all approach. This also applies to intermittent fasting.
Generally speaking, women should take a more relaxed approach to fasting than men. This may include shorter fasting periods, fewer fasting days, and/or consuming fewer calories on the fasting days.
Here are some of the best types of intermittent fasting for women:
- Crescendo method: Fasting 12–16 hours two to three days a week. Fasting days should be nonconsecutive and spaced evenly across the week (for example, Monday, Wednesday, and Friday).
- Eat-stop-eat (also called the 24-hour protocol): A 24-hour full fast once or twice a week (maximum of two times a week for women). Start with 14–16 hour fasts and gradually build up.
- The 5:2 diet (also called “The fast diet”): Restrict calories to 25% of your usual intake (about 500 calories) for two days a week and eat “normally” the other five days. Allow one day between fasting days.
- Modified alternate-day fasting: Fasting every other day but eating “normally” on non-fasting days. You can consume 20–25% of your usual calorie intake (about 500 calories) on a fasting day.
- The 16/8 method (also called the “Leangains method”): Fasting for 16 hours daily and eating all calories within an eight-hour window. Women are advised to start with 14-hour fasts and eventually build up to 16 hours.
Whichever you choose, it is still important to eat well during the non-fasting periods. If you eat many calorie-dense foods during the non-fasting periods, you may not experience the same weight loss and health benefits.
At the end of the day, the best approach is one that you can tolerate and sustain in the long term, and that does not result in any negative health consequences.
How to get started with intermittent fasting
Chances are you’ve already done many intermittent fasts before. Many people instinctively eat this way, skipping morning or evening meals.
The easiest way to get started is to choose one of the intermittent fasting methods above and give it a go. However, you don’t need to necessarily follow a structured plan.
An alternative is to fast whenever it suits you. Skipping meals from time to time when you don’t feel hungry or don’t have time to cook can work for some people.
At the end of the day, it doesn’t matter which type of fast you choose. The most important thing is to find a method that works best for you and your lifestyle.
Safety and side effects
Modified versions of intermittent fasting appear to be safe for most women.
That being said, a number of studies have reported some side effects, including hunger, mood swings, lack of concentration, reduced energy, headaches, and bad breath on fasting days.
There are also some stories online of women who report that their menstrual cycle stopped while following an intermittent fasting diet.
If you have a medical condition, you should consult with your doctor before trying intermittent fasting.
Medical consultation is particularly important for women who:
- Have a history of eating disorders
- Have diabetes or regularly experience low blood sugar levels
- Are underweight, malnourished, or have nutritional deficiencies
- Are pregnant, nursing, or trying to conceive
- Have fertility problems or a history of amenorrhea (missed periods)
At the end of the day, intermittent fasting appears to have a good safety profile. Yet, if you experience any problems — such as loss of your menstrual cycle — stop immediately.
The bottom line
Intermittent fasting is a dietary pattern that involves regular, short-term fasts.
The best types for women include daily 14–16 hour fasts, the 5:2 diet, or modified alternate-day fasting.
While intermittent fasting has been shown to be beneficial for heart health, diabetes, and weight loss, some evidence indicates it may negatively affect reproduction and blood sugar levels in some women.
That being said, modified versions of intermittent fasting appear safe for most women and may be a more suitable option than longer or stricter fasts.