Fasting is showing up more and more often in popular culture. It’s been discussed in best-selling books, and celebrities from Jimmy Kimmel to Hugh Jackman have endorsed it as a way to promote weight loss and better sleep. But what is fasting, and is there science to back up the claims about its benefits? The New York Times tackled both of these questions in their Well blog. Here is what you need to know:

• What is fasting? Essentially, fasting is not eating for an extended amount of time. That being said, there are a few ways to fast. Fasting might mean skipping certain meals, or fasting intermittently—alternating between days of fasting and eating. The 5:2 diet follows the second model: it calls for dieters to eat a normal amount of calories for five days, and then to eat a restricted amount of calories (500 for women, 600 for men) on each of the other two days.
• What does science say? Celebrities aren’t the only ones who are fond of fasting. While the scientific community as a whole is still in disagreement over the value of fasting, a few researchers believe that a growing body of evidence suggests it may be beneficial. In one study, these researchers found intermittent fasting promoted more weight loss, muscle retention, and blood sugar stability than a low-calorie diet. Animal studies suggest intermittent fasting may lower the risk of some chronic diseases and increase lifespan. Mark Mattson, a neuroscientist at the National Institute of Aging who practices intermittent fasting himself, also notes that fasting makes sense from an evolutionary perspective—since food was often scarce for much of human history, our bodies evolved to help us go for extended periods of time without eating.

So, with all of these endorsements, are there any downsides to fasting? The New York Times did mention one—fasting can be hard to do. In one research programme on fasting, 10 to 20 percent of the participants dropped out because they couldn’t stick with the programme. However, don’t get discouraged by these numbers. It’s normal to feel a little off your game until your body adapts, which can take two weeks to a month, according to Dr. Mattson. If you want to give fasting a try, be sure to talk with your doctor first to find the fasting-style that works with your particular goals and lifestyle.

Source: New York Times