When people don't eat for 3 days, the blood flow to their arms increases significantly, almost doubling from normal levels.

When men and women don't eat for 3 days, men tend to have higher levels of blood pressure, blood flow to arms, calorie burning rate, and stress hormones than women, but both sexes respond similarly to fasting.

When people don't eat for 3 days, their body burns calories at a slightly higher rate for about a day and a half, then returns to normal levels.

When people don't eat for 3 days, their adrenaline levels go up, but not until after the second day of fasting.

When people don't eat for 3 days, their insulin levels drop significantly, which is part of the body's adaptation to fasting.