Do you want to eat snacks after a short night? It is not only about willpower. Two hormones control hunger.

Ghrelin says, "I'm hungry!" Leptin says, "I'm full." In a 2004 study, young men slept only four hours for two nights.

After that, their ghrelin went up and their leptin went down. They felt hungrier and wanted sweet and starchy food. So, good sleep can help you eat well.

Many people find it hard to stop eating snacks after a night of little sleep, and hormones may be partly responsible. Our appetite is mainly controlled by ghrelin, which tells us we are hungry, and leptin, which tells the brain we have enough energy. In a 2004 study at the University of Chicago, 12 healthy young men slept four hours for two nights and, on another occasion, spent ten hours in bed for two nights.

After short sleep, leptin fell by about 18 percent and ghrelin rose by about 28 percent. The men also felt about 24 percent hungrier and especially wanted foods rich in carbohydrates. A later review found that people with restricted sleep ate about 385 extra calories a day.

Craving snacks after a short night is often blamed on weak willpower, but research suggests that biology plays a role. Appetite is regulated largely by two hormones: ghrelin, released mainly by the stomach to signal hunger, and leptin, produced by fat cells to signal that energy stores are sufficient. In a 2004 crossover study, 12 healthy young men spent two nights with four hours of sleep and two nights with ten hours in bed.

After sleep restriction, leptin dropped by about 18 percent, ghrelin rose by about 28 percent, and hunger increased by about 24 percent, with a particular desire for carbohydrate-rich foods. Brain imaging later showed that after a night without sleep, activity in frontal regions involved in judgment weakened while the desire for high-calorie foods grew. A 2017 meta-analysis found that sleep-restricted participants consumed about 385 extra calories per day without burning noticeably more. But the original hormone study was small and brief, and later experiments have not consistently reproduced the hormonal changes. Overeating itself appears more reliable than any single hormonal explanation.