What is intermittent fasting, and is it healthy?

Story highlights

  • Intermittent fasting is occasional starvation done in a strategic way
  • Experts say it can improve your overall health, but talk to your doctor before trying it

When you hear the word "fasting," you probably think of gimmicky diets—and, um, feeling "hangry." But a growing body of research suggests that cycling super low-calorie days into your normal eating plan could potentially improve your health (more on that later). But before you skip lunch and let your gut start growling, read on for everything you need to know about intermittent fasting.

    What is intermittent fasting (IF)?

    In very basic terms, IF is occasional starvation done in a strategic way. The idea is to cycle between periods of regular eating and fasting, during which you severely restrict your calorie intake or don't consume any food at all. Some people fast for hours, while some may go for a full day or longer.

    Fasting isn't one size fits all

    IF may mean something different depending on who you talk to. One of the more commonly known fasting systems is the 5:2 diet, which involves restricting calories for two non-consecutive days a week and eating without calorie restraints on the other five days. (Jimmy Kimmel credited the 5:2 diet with his weight loss in a Men's Journal story last year.)
    Others may fast on a day-to-day basis by eating only during a specific time window. Mark Mattson, a neuroscientist at the National Institute on Aging in Maryland who has researched the subject extensively, shared with the New York Times that most days he skips breakfast and lunch and eats all of his calories within a six-hour window starting in the afternoon. And, Hugh Jackman revealed that he fasted for 16 hours and ate within an 8-hour window to get in shape for his role as Wolverine in 2013.

    The health benefits of fasting go beyond weight loss