After fasting for 3 days, your body has trouble handling sugar when you eat it again, causing higher blood sugar and insulin spikes.

When you go without eating for 3.5 days, your body starts releasing more fat into your bloodstream than after just a half-day fast—even if your insulin levels are the same—because your fat cells become less responsive to insulin’s ‘stop releasing fat’ signal.

When you don't eat for about 3.5 days, your body switches to burning fat for energy—so it stops listening to the hormone that tells fat cells to stop breaking down, and starts listening more closely to the hormone that tells them to break down faster.

Non-consecutive 24-hour fasting three times per week improves glucose tolerance.

When healthy adults don’t eat for 3.5 days, their bodies start breaking down fat for energy—even though the usual fat-burning hormones and blood sugar levels stay pretty much the same.

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.