Trisha Pasricha, MD

Many of my friends have been trying intermittent fasting for weight loss. Does it work, and is it better than other diets?

Intermittent fasting has been shown to lead to some weight loss in several studies. But it might not work better than other dieting practices.

When scientists compared intermittent fasting to simply eating fewer calories throughout the day, they found that intermittent fasting wasn’t more effective in helping people shed pounds.

Conventional dieting focuses on what you eat, but intermittent fasting focuses on the time you eat it - within an eight-hour window per day, for example. Because intermittent fasting doesn’t typically require monitoring calories or changing what you eat, it can feel easier to stick with.

Interest in the practice took off in the last decade or so, after experiments in animals showed that eating restricted to certain times had a profound impact on metabolic health and the microbiome. But in people, the weight-loss benefits linked to intermittent fasting may be because they took in less food in general - up to 550 fewer calories per day.

Both intermittent fasting and overall calorie restriction approaches can result in weight loss for a few months, but they are very hard to sustain; studies have shown that some of that weight comes back after a year, regardless of the approach.

Given all these factors, intermittent fasting is not my go-to recommendation for healthy eating. Instead, I suggest the Mediterranean diet, which has been better studied for improving your heart health and lowering the risk of Type 2 diabetes. Because of the diet’s higher fiber and healthier fat intake, you may lose a bit of weight - even if you aren’t thinking about cutting calories.

How does intermittent fasting work?

Intermittent fasting can take on many forms, each with potentially different impacts on our health. There are two common variations:

The 5:2 approach

In this method, people each week severely restrict calories by at least 75 percent for two usually nonconsecutive days, and then eat without restrictions for five days.

A striking 2024 study published in JAMA Network Open looked at 5:2 intermittent fasting for overweight or obese adults with newly diagnosed Type 2 diabetes. Researchers found that intermittent fasting led to more weight loss (on average 21 pounds after 16 weeks) compared to eating as usual and taking prescription drugs for diabetes. It also led to greater improvements in HbA1c, a long-term measure of blood sugar levels.

But it’s important to know that in this study, the intermittent fasting group consumed one prepackaged low-energy meal replacement per day that the control group on diabetes medication did not. That means the control group was likely consuming more calories.