What is Intermittent Fasting?

Intermittent fasting (IF) often involves a daily cycle of fasting and feeding. IF is an umbrella term that refers to at least three different approaches to restricting calories intermittently. These include alternate day fasting, which involves eating fewer than 500 calories every other day, the 5:2 approach to fasting, which involves two fast days of fewer than 500 calories per week, and time-restricted feeding, which involves eating within a narrow 8-10-hour window each day.

A popular time-restricted feeding approach is the 16:8. This involves fasting during a 16-hour window and eating during an 8-hour window, either every day or several days per week. During your 8-hour eating window, for example from 10 a.m. to 6 p.m., you don’t have to count calories or necessarily change the way you eat. You simply confine any calories you consume to this window.

“It’s important to remember that with intermittent fasting, you do typically get to eat at least a little bit every day,” Dr. Krista Varady says. “There’s also no limitation on types of food or number of calories you eat during your feeding windows or ‘feast’ days.”