If you sleep less than 7.7 hours a night, the less you sleep, the higher your body mass index (BMI) tends to be — for example, people who sleep 5 hours have a 3.6% higher BMI than those who sleep 8 hours, even when you account for their age, gender, or breathing issues during sleep.

If you cut your sleep down to just two-thirds of what you normally get for eight days straight, you’ll likely eat about 559 extra calories a day without moving more—this could be why people who don’t sleep enough tend to gain weight.

After 24 hours without sleep, heart rate drops slightly but then starts rising again over the next 8 hours, suggesting the body's response to sleep loss changes over time.

The heart's ability to pump blood per minute per body area remains stable even after 32 hours without sleep in healthy men.

After one night without sleep, average blood pressure rises by about 4 points and stays elevated for up to a day and a half in healthy men.

After staying awake for a day, healthy men in their early 30s with average weight experience a small but noticeable rise in blood pressure that stays elevated for up to a day and a half.