Losing Even an Hour of Sleep a Night Is Linked to Weight Gain

The optimum amount of sleep varies by individual, but most people need between seven and nine hours a night. In this study, the researchers instructed 95 people, who normally slept around 7.5 hours a night, to go to bed 1.5 hours later than usual for six weeks, while getting up at the same time. They wore wrist monitors and had their blood hormone levels tested, among other measures, to assess any changes happening over the course of the study. 

The sleep-deprived participants gained about a pound over the six-week period, and their levels of leptin, a hormone linked to body fat, went up. “We found that they spent more time being sedentary during this period of sleep restriction compared to the period of adequate sleep,” says St-Onge. They were awake for longer, but they were less apt to use that time for exercise or moving around.

The results mesh well with what was already known about sleep and body weight from more extreme experimental studies, says Dr. Sirimon Reutrakul, an endocrinologist and professor of medicine at the University of Illinois College of Medicine who was not involved in the study.