The newest celebrity fad diet isn’t exactly “new,” considering it’s been around since Biblical times. Indeed, from Jimmy Kimmel to Benedict Cumberbatch, fasting has become the new sanctioned diet of the stars — and for good reason. Unlike many other trending diets, responsible fasting is backed by a wealth of compelling and scientifically-founded benefits.
Intermittent fasting — also known as the 5-2-5 diet — involves five days of normal eating followed by two days of severe calorie restriction. In many ways, this diet goes against everything Westerners have come to understand about eating and health.
“Most people are putting something in their mouths essentially every waking hour,” says Mark Mattson, a neuroscientist and researcher at the National Institute on Aging in an interview with Time. “But from an evolutionary perspective that’s not how people or animals are genetically geared to eat.”
And while this might not be a diet that comes easy, the benefits of intermittent fasting are plentiful. For example, in a 2010 study, obese women who fasted two days a week for six months dropped nearly 13 pounds. The women were allowed around 600 calories of food on fasting days, including vegetables, fruit, and small portions of skim milk. Compared with women who traditionally dieted, the women who fasted lost more weight and a higher body fat percentage.
This happens because fasting gives your body a chance to deplete its stores of glycogen, which is a form of energy that your body stores for later use. When you’re constantly eating, glycogen is continually present in your liver, meaning that it remains within your fat cells.
Meanwhile, if your body goes without food for 12 hours, your liver runs out of glycogen, resorting to energy from the glycogen stored in fat cells.
Despite its benefits, intermittent fasting certainly isn’t for everyone. Consuming one to two servings of fruit and two and a half servings of vegetables a day, combined with regular exercise, is another perfectly adequate means to achieving a healthy body weight.