How many calories end a fast?

Expert insight:

Because the body converts every calorie into fuel, even the smallest amount will put you in an eating period, says Adam Feit, CSCS, performance nutrition coordinator for Precision Nutrition in Springfield, Massachusetts. “During a fast, you want the body to use the stores that are already there, including glycogen from muscle tissue.” Once you take in calories, you won’t get all the benefits (such as fat loss and fewer signs of aging) of running on those reserves.

To ease hunger pains, Feit recommends hydrating with zero-calorie beverages—that means no coffee with milk. “Having more liquids in the body will give you that feeling of fullness.”

The bottom line:

If you’re still dying for a 50-calorie break (or you’re feeling weak or fatigued), you may have changed your habits too quickly. To make fasting more sustainable, Feit suggests lengthening your non-eating periods over a week or more until they’re between eight and 16 hours long. Expect to feel hungry during the first few weeks on your new schedule.