What is intermittent fasting?

What is intermittent fasting?

Many diets focus on what to eat, but intermittent fasting is all about when you eat.

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.

Johns Hopkins neuroscientist Mark Mattson has studied intermittent fasting for 25 years. He says 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, it was easier to maintain a healthy weight. Johns Hopkins dietitian Christie Williams, M.S., R.D.N., explains: “There were no computers, and TV shows turned off at 11 p.m.; people stopped eating because they went to bed. Portions were much smaller. More people worked and played outside and, in general, got more exercise.”

Nowadays, TV, the internet and other entertainment are available 24/7. We stay awake for longer hours to catch our favorite shows, play games and chat online. We’re sitting and snacking all day — and most of the night.”

Extra calories and less activity can mean a higher risk of obesity, type 2 diabetes, heart disease and other illnesses. Scientific studies are showing that intermittent fasting may help reverse these trends.
How does intermittent fasting work?
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.

Mattson says that after hours without food, the body exhausts its sugar stores and starts burning fat. He refers to this as metabolic switching.

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