If you fast every day for 16 hours and eat for 8 hours, your body's energy-burning rate starts to slow down after 2-3 weeks.

Skipping meals intermittently for two weeks didn’t change how the body uses sugar, fat, or muscle protein in healthy, lean people—even when their insulin levels were raised.

After two weeks of skipping meals intermittently, the body burns fewer calories at rest—which could make you gain weight if you keep eating the same amount.

People with metabolic syndrome who try intermittent fasting lose about 4 pounds on average after a few months, even without counting calories.