Intermittent fasting is an eating plan that switches between fasting and eating on a regular schedule. Research shows that intermittent fasting is a way to manage your weight and prevent — or even reverse — some forms of disease. But how do you do it? And is it safe?

With intermittent fasting, you only eat during a specific time. Fasting for a certain number of hours each day or eating just one meal a couple days a week, can help your body burn fat. And scientific evidence points to some health benefits, as well.

Many studies shows that our bodies have evolved to be able to go without food for many hours, or even several days or longer. In prehistoric times, before humans learned to farm, they were hunters and gatherers who evolved to survive — and thrive — for long periods without eating. They had to: It took a lot of time and energy to hunt game and gather nuts and berries.

Even 50 years ago there were no computers, and TV shows turned off at 11 p.m

Portions were much smaller. More people worked and played outside and, in general, got more exercise.

There are several different ways to do intermittent fasting, but they are all based on choosing regular time periods to eat and fast. For instance, you might try eating only during an eight-hour period each day and fast for the remainder. Or you might choose to eat only one meal a day two days a week. There are many different intermittent fasting schedules.

After hours without food, the body exhausts its sugar stores and starts burning fat. We refers to this as metabolic switching. 

Intermittent fasting contrasts with the normal eating pattern for most Americans, who eat throughout their waking hours.

If someone is eating three meals a day, plus snacks, and they’re not exercising, then every time they eat, they’re running on those calories and not burning their fat stores.

Intermittent fasting works by prolonging the period when your body has burned through the calories consumed during your last meal and begins burning fat.