Intermittent Fasting, Decoded

What it is, why it works, and how to do it safely.

- LISA TURNER

You’ve heard about intermittent fasting for weight loss, blood sugar control, and other health benefits. And it’s not just the latest in a long line of fad diets. Research shows that periodic fasting encourages weight loss (especially reductions in belly fat) and, done the right way, protects against disease, improves overall health, and enhances longevity. When done poorly, however, intermittent fasting can leave you dehydrated, fatigued, and lacking in vital nutrients. Here’s what you need to know, and how to do it safely.

The Basics

Intermittent fasting is an eating routine that restricts or eliminates daily food consumption to a specific window of time in a very specific pattern. It’s nothing new. Fasting has been used by various cultures throughout history for therapeutic and spiritual purposes. And in primitive times, humans didn’t have 24/7 access to food and were forced to fast, sometimes for days. As a result, our bodies evolved to survive—and thrive— without eating for extended periods of time. So in spite of our obsession with food, we humans can function well, and benefit greatly, from periodic fasting.

Because it naturally restricts calories (unless you binge during your eating periods), intermittent fasting encourages weight loss. Abstaining from food also prompts physiological changes that boost metabolism, making stored body fat more accessible and promoting weight loss—especially in the abdominal area— while retaining lean muscle. Studies show that periodic fasting can often lead to significant decreases in weight and body fat, with less muscle loss than standard calorie-restricted diets, and, in some studies, as much as a 7 percent reduction in waist circumference (belly fat).