Intermittent fasting for women: Expert answers to your top questions

• Intermittent fasting can be an effective way for healthy women to lose weight.
• There is some evidence that intermittent fasting boosts longevity and health.
• However, more research is needed to understand how intermittent fasting affects hormones in women.

Intermittent fasting is a relatively straightforward method for women to try to lose weight—and that’s why it’s so popular. Compared to other diets and programs, intermittent fasting has simple rules and flexibility to tailor to your lifestyle. 

But if you’re curious about intermittent fasting, you probably have a few questions. Does it work for women? Is it right for all age groups? How does it affect your hormones? 

We spoke with our in-house expert, Kendra Gutschow, RDN (registered dietitian nutritionist), to get answers to your most common questions.

Note: Consult with your medical provider before making dietary changes.

A brief review of intermittent fasting

Before we tackle the questions, here’s a quick rundown on intermittent fasting.

Intermittent fasting is an eating pattern that focuses on when you eat rather than what you eat. For example, one popular eating schedule allows food and drink within an 8-hour window (between 10 a.m. to 6 p.m.) and fasting during the other 16 hours of your day. 

It’s thought that switching between eating and fasting windows helps you reduce the calories you eat throughout the day, which can lead to improved health and weight loss. 

Does intermittent fasting work for women? 

Science says yes, intermittent fasting can be an effective strategy for weight loss for many people. Studies and reviews have also found it’s typically safe for the majority of women when done under the supervision of a doctor.

For most healthy adult women, Gutschow says that intermittent fasting has few safety concerns. However, there are important exceptions, including women who are pregnant or breastfeeding, which you can read about below.

What are the benefits of intermittent fasting for women?

If you’re interested in intermittent fasting, weight loss is probably your main goal—and weight loss is one of several possible perks. Let’s explore potential benefits in more detail. 

1. Weight loss

It’s thought that extended fasting periods in intermittent fasting may encourage fat loss by triggering what’s called a lipolysis response. This means when you fast, your body runs out of sugar stores for energy, and must tap into fat reserves to get what it needs, which ultimately helps you lose weight.

You might be wondering if intermittent fasting is any better than standard weight loss advice, which suggests eating within a calorie deficit, or burning more calories than you consume.

A small study exploring the safety and efficiency of intermittent fasting dug into this idea. The study compared the results of participants on time-restricted fasting plans with those eating in calorie deficits. 

After one year, they found there wasn’t a significant difference between the two groups in regard to weight loss or risk factors. This research suggests intermittent fasting may be just as safe and effective as eating in a caloric deficit for helping you lose weight. 

2. Lower risk of heart disease

Intermittent fasting might help boost your heart health by lowering LDL (“bad”) cholesterol and blood pressure. 

Even without added exercise, patients in one study found that LDL cholesterol was lowered during intermittent fasting. Lower cholesterol helps reduce your risk of coronary heart disease and stroke.  

In the same study, participants had significant reductions in blood pressure when intermittent fasting. According to the American Heart Association, lowering your blood pressure can help you reduce your risk of heart failure, heart attack, and stroke. 

3. Longevity

In a small study examining longevity, the results suggested intermittent fasting may help you live a longer, healthier life by reducing risk factors for age-related diseases (such as type 2 diabetes, cancer, and heart disease).

4. Brain health

Research also offers some hope that intermittent fasting may have anti-aging and mood-boosting effects on the brain. 

A recent review of animal studies also has researchers cautiously optimistic about using fasting for the possible treatment and prevention of Alzheimer’s Disease. 

Results suggest that intermittent fasting may reduce the amount of beta-amyloid in the brain of mice. Too much of this naturally occurring substance can cause plaque buildup in the brain, which may contribute to Alzheimer’s Disease.

Take the Alzheimer’s benefits with a grain of salt, however, as researchers are still grappling with the causes of Alzheimer’s.

5. PCOS symptom relief

According to research, women with polycystic ovarian syndrome (PCOS) may experience fewer symptoms associated with PCOS when on an intermittent fasting schedule. 

Over 73% of participants in one small study experienced an improvement in menstrual cycle regularity, and the study suggested that time-restricted eating schedules may help reduce chronic inflammation and body fat.

But there is a catch: 

According to the CDC, “women with PCOS are often insulin resistant,” meaning their bodies aren’t as efficient at using insulin to reduce blood glucose. Gutschow does not recommend intermittent fasting for women who have problems with blood sugar stability.

Although women in another small study experienced a slightly impaired glucose response after meals, individuals in this study fasted for a full 24 hours every other day for three weeks—longer than the most common intermittent fasting plans. 

Gutschow also does not recommend fasting for 24 hours or longer—and how long you fast does seem to make a difference. Other research suggests 12-hour fasts had no significant impact on participants’ fasting glucose or insulin.

Who should avoid intermittent fasting? 

Intermittent fasting isn’t a one-size-fits-all approach to weight loss. Whether or not you should avoid intermittent fasting comes down to your specific health needs and lifestyle choices. 

Before diving in, consider how well it will work for your lifestyle. If you prefer eating small meals throughout the day, for example, it may be difficult to switch to large meals within short fasting windows. 

Women with certain health conditions or in specific circumstances should also avoid intermittent fasting. Gutschow does not recommend intermittent fasting for women who:

• Have a history of blood sugar instability.
• Are currently on medication or insulin to control blood sugar.
• Are pregnant or breastfeeding.
• Are at risk for gallbladder disease.

You should also skip intermittent fasting if you have a history of eating disorders or disordered eating, as it can increase the risk of disordered eating. 

Not sure if intermittent fasting is right for you? Chat with your doctor for guidance.

How does intermittent fasting affect hormones in women? 

While intermittent fasting offers plenty of overall health benefits, we don’t have extensive research about how it impacts hormones in women. Some studies show promise for improving hormonal health, while others offer conflicting results. 

Our suggestion? Again, talk to your doctor before beginning intermittent fasting if you have any concerns or a history of hormonal issues. 

Thyroid hormones

Both rodent and human studies suggest intermittent fasting can lower a thyroid hormone called serum T3 (or triiodothyronine), which boosts energy expenditure. 

In mice, this research also points to a possible reduction in thyroid stimulating hormone and hypothalamic thyrotropin-releasing hormone. Whether or not this happens in humans is still unclear. 

Stress hormones

Studies in humans and rodents suggest that intermittent fasting may increase levels of the stress hormone cortisol, as well as how often it is secreted. 

Research suggests that chronically elevated cortisol can lead to weight gain. It’s also true that research links cortisol to increased stress and nervousness.

It’s easy to assume cortisol is always bad, especially since it’s classified as a stress hormone—but cortisol is also a healthy part of your everyday life. 

Cortisol surges after you wake up in the morning as a normal part of your circadian rhythm, and research suggests this spike gives you an energy boost to get through your day. 

One study suggests that increased cortisol during stressful situations may also help you deal with challenges and reduce negative emotional responses.

Testosterone

A review of human trials suggests that intermittent fasting reduces testosterone levels in women, especially if eating periods end before 4 p.m.

Is this drop in testosterone good? That varies by person. 

In a small study analyzing the effects of intermittent fasting on PCOS, for example, the drop in total testosterone experienced by participants was considered beneficial. This may or may not be the case for women with normal or low testosterone levels—if you have concerns, it’s always a good idea to check with your doctor. 

Estrogen

In a recent animal study, the estrogen levels of female rats were significantly higher after two weeks of alternate-day fasting. Like the study suggesting impaired glucose response in women, however, fasting periods were a full 24 hours every other day, which Gutschow does not recommend. 

A recent review of human trials suggests that common intermittent fasting schedules probably don’t have a significant effect on estrogen levels in women.

Is intermittent fasting right for women over 50? 

Gutschow is the first to admit that more research is needed on intermittent fasting for older women, but that doesn’t mean healthy, older women can’t give it a try. 

One concern to be aware of in older adults is lost muscle mass that may happen when you fast. Loss of muscle mass may also be a cause for reduced metabolism in older adults. 

The good news is that age-related muscle loss can be avoided with regular physical activity. An app like Noom Weight can help you stay on top of physical activity by logging how much you exercise each day. 

What is the best intermittent fasting schedule for women?

While there’s no “ideal” schedule, the best intermittent fasting plan for women is one that aligns with your health goals and one you’ll stick with. Here are two common types of intermittent fasting patterns:

• The 16/8 method: Eat normally during an 8-hour window, then follow up with a 16-hour period of fasting.

• The 5:2 method: Follow your normal eating pattern five days per week, then limit yourself to a single 500–600 calorie meal during the other two days.

There are also other patterns that are more extreme:

• Alternate-day fasting: Eat as you normally do during non-fasting days, then have one or two 24-hour fasts on nonconsecutive days. 

• Warrior diet: Eat very little during the day, then have one large meal in the evening. This pattern recommends eating 80% to 90% of your calories during a 4-hour window. 

However, not every intermittent fasting pattern is considered healthy—and you should approach any extreme fasting schedule with caution. Gutschow recommends discussing any plans with your doctor first and avoiding patterns with fasts of 24 hours or longer.

What can women eat while intermittent fasting?

A common misconception is that following an intermittent fasting plan allows you to eat plenty of calorie-dense, low-nutrient foods and still lose weight. After all, the plan focuses on when you eat, not what you eat. 

Experts disagree. 

A calorie deficit (also called caloric deficit) is key to any weight loss program. To lose weight, you need to eat fewer calories than you burn. 

While it’s true that intermittent fasting alone can lead to a reduction in daily calories, there’s no guarantee. If you’re not paying attention to what you eat, chances are your caloric intake will fluctuate.

To feel your best, Gutschow suggests eating satisfying, nutritious foods. Think lean proteins, healthy fats, and fresh fruits and vegetables. 

Noom Weight uses the calorie density principle to simplify how you choose foods. This principle tells us that some foods have more calories per gram than others. By learning which foods have a lower calorie density, you can fill up on nourishing, satisfying choices while still leaving room for your favorite treats. 

When you follow the calorie density principle, you can also let go of outdated ideas, like labeling foods as “good” and “bad.” All foods are welcome in moderation.

Your best bet? Track what you eat to make sure you stay within your ideal calorie range for weight loss and try to strike a balance between satisfying, healthy foods and your favorite treats. 

When your efforts are consistent, you’re more likely to reach your weight loss goals. 

Not sure where to start? We break down how to pick satisfying, wholesome foods during your eating window.

How to get started with intermittent fasting

Ready to try intermittent fasting for yourself?

We suggest experimenting with plans and implementing small, sustainable steps—like incorporating whole foods into your meals and adding a little movement to your day. 

If you need extra support, Noom Weight can help. Check out our guide: Noom Weight for Intermittent Fasting.