Intermittent fasting – periods of voluntary abstinence from food and drink – is a broad term that can be applied to many different practices. This type of dieting has spurred many books and received a lot of attention in the last few years since studies (mostly in animals) have shown that it may reduce the risk for several diseases as well as promote weight loss. Additional research, including a small study of four fasting people published in Scientific Reports in 2019, suggests that intermittent fasting may also help boost metabolism.
The most popular approach to intermittent fasting is the 16/8 approach, which requires fasting for 16 hours a day; you’d eat between, say, 11:30 a.m. and 7:30 p.m. Another version, alternate-day fasting (ADF), alternates 24-hour periods of fasting (which are actually very restricted 500-calorie diets) with days of eating freely. The 5:2 approach limits fasting to just two days a week, while the Warrior Diet follows a 20-hour fast with one large meal consumed at night. “Part of the confusion with intermittent fasting lies in the lack of a definition,” says Robin Foroutan, RDN, a New York City-based registered dietitian nutritionist and spokesperson for the Academy of Nutrition and Dietetics. “To some people, intermittent fasting means that they fast every day, while to others it means they only eat between 11 a.m. and 6 p.m.” (Here’s everything you need to know about the Warrior Diet.)