Intermittent fasting has gotten a lot of attention recently—everyone from celebrities to social media influencers is talking about it.
The idea is that by limiting the time during the day when you can eat, you can lower your calorie intake and maybe lose weight. But does it actually work? Is it healthy? We answer these questions and more in a roundup from the National Institutes of Health (NIH).
What is intermittent fasting?
Also called time-restricted feeding, intermittent fasting is when people restrict the time during the day when they can eat. For example, someone may eat only during a 12-hour time period, such as 7 a.m. to 7 p.m.
Can it help you lose weight?
Many people choose intermittent fasting as a way to lose weight. And some early NIH research supports this, says Charlotte Pratt, Ph.D., RD, of the National Heart, Lung, and Blood Institute. "In studies, people were able to demonstrate some changes in terms of body weight following a time-restricted eating plan," Dr. Pratt explains. Research in animals has shown that calorie reduction can slow down aging and prevent some diseases. However, more research needs to be done in humans before the health benefits—and risks—are fully understood.
Does what you eat when fasting matter?
The timing of meals should not be the only factor in trying to lose weight or becoming healthier, Dr. Pratt notes. What and how much you eat are also important. Current U.S. dietary guidelines recommend eating a diet rich in fruits, vegetables, and whole grains. Dr. Pratt says that most adults should also do at least 150 to 300 minutes (2 1/2 to 5 hours) a week of moderate-intensity, preferably aerobic activity that is spread throughout the week.
Is it safe?
It is not safe for everyone, especially those with health conditions like diabetes, kidney disease, or heart-related issues. "Intermittent fasting should be approached individually and with the help of a dietitian or physician," Dr. Pratt says. As with all diets, you should talk with your doctor or other health care provider before you try it. Your provider can review your health history and medication list and help you decide which eating plan and exercise schedule is best for you.
What future research is NIH planning to do?
One NIH clinical trial that is currently recruiting participants focuses on the effects of intermittent fasting on nonalcoholic fatty liver disease. Participants will be allowed to eat a set number of calories between 8 a.m. and 4 p.m. every day. Throughout the study, researchers will look for changes in certain fat levels, body weight, and other health indicators.
Another NIH-supported clinical trial will study whether time-restricted feeding can help improve insulin resistance and reduce weight in women with polycystic ovary syndrome, or PCOS. Dr. Pratt notes that this study will take place over 16 weeks and is expected to be completed at the end of 2021.