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 noradrenaline levels go up, but not until after the second day of fasting.

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 insulin levels drop significantly, which is part of the body's adaptation to fasting.

Metabolic rate increases during 24-36 hour fasts due to norepinephrine and adrenaline release, but does not continue to increase beyond 36 hours of fasting.