Lose sleep, gain weight

Not getting your full seven or eight hours of sleep every night could make you put on weight. Even small disruptions to your sleep pattern can increase your calorie intake and lead to weight gain, a new study has found.

People who lost around 80 minutes of sleep a night put on 1 lb (0.45 kg) by the end of the six-week study. The weight gain came from eating more, not from changes in metabolism or exercise.

The mechanism isn’t clear. There doesn’t seem to be a direct causal relationship between insomnia and weight gain. Instead, people tend to eat more, especially late at night, when they’re tired.

The behavior has been seen in people with bad insomnia who sleep for no more than four hours a night. But this new study suggests that even relatively small amounts of sleep disruption can trigger the same pattern.

They tested the idea on 95 volunteers who usually slept seven or eight hours a night. The participants were randomly assigned to either maintain their normal sleep or reduce it by about 80 minutes a night for six weeks.

In an earlier study of the same group, women who lost around 80 minutes sleep each night started to eat about 270 more calories a day.

Ann Intern Med, 2026; 179(8): 1085 to 1093