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Going to bed a little later each night may seem harmless, but new research suggests that a modest, repeated loss of sleep could be enough to affect body weight and daily activity levels within weeks.
Researchers at Columbia University found that adults who slept about 80 minutes less per night gained an average of one pound over six weeks and spent more time being sedentary compared with when they followed their usual sleep schedule. The study suggests that the kind of mild sleep loss experienced by many Americans—not just extreme sleep deprivation—may contribute to obesity risk over time.
The study, published July 6 in the Annals of Internal Medicine, included 95 adults who typically slept between seven and eight hours a night. Participants completed two six-week study periods: one in which they maintained their normal sleep schedule and another in which they delayed bedtime by 90 minutes, reducing their sleep by an average of about 80 minutes per night.
Throughout both phases, participants wore wrist monitors that tracked their sleep and activity, while researchers measured body weight, waist circumference, body composition and fasting hormones involved in appetite regulation.
By the end of the sleep-restriction phase, participants had gained an average of one pound. They also spent an additional 17 minutes per day being inactive. Among men and postmenopausal women, sedentary time increased by nearly 30 minutes a day.
The increase in inactivity could not simply be explained by participants being awake for longer.
“Even when we accounted for the fact that they were awake longer when sleep was shortened, participants spent more time being inactive than when they got adequate sleep,” first author Faris Zuraikat, assistant professor of nutritional medicine at Columbia University’s Department of Medicine and Institute for Human Nutrition, said. “This is notable, as people who are more sedentary have elevated risk for chronic diseases.”
The researchers said the findings are particularly important because most previous studies have focused on severe sleep deprivation, often limiting people to around four hours of sleep a night. Their goal was to determine whether the more common pattern of chronic, mild sleep loss—estimated to affect about 30 percent of adults—could also influence body weight.
Teresa Power, a board-certified clinical sleep health specialist and founder of Sleep Better NYC LLC, who was not involved in the research, told Newsweek that even one poor night’s sleep can alter hormones that regulate hunger and metabolism.
“Sleep loss immediately impacts hormone levels, including ghrelin, leptin, insulin and cortisol,” she said. “You may feel hungrier but less satisfied when you eat. It also increases activity in the brain’s reward centers, making high-calorie, sugary and fatty foods much more tempting, especially later in the day.”
Power added that poor sleep can also impair communication between the emotional and logical parts of the brain, making healthy food choices and regular exercise more difficult.
Lead study author Marie-Pierre St-Onge, professor of nutritional medicine at Columbia University, said the findings suggest sleep should be considered alongside diet and exercise when addressing weight gain.
“Our study shows that getting adequate sleep may help reduce the risk of weight gain and obesity-related conditions like heart disease and diabetes,” she said. “People tend to gain weight over the course of adulthood, and focusing on eating a healthier diet and getting more physical activity to offset weight gain is simplistic and can be difficult to maintain.”
While the average weight gain was relatively small, Zuraikat said the timeline is significant.
“While the one-pound weight gain observed with modest sleep curtailment is not overwhelming, it is important to remember this is occurring over just six weeks,” he said.
Power added that some groups appear especially vulnerable to the effects of sleep loss on weight and metabolism, including people with high stress levels, shift workers, those with untreated sleep apnea and individuals who are already overweight. Women during menopause and post-menopause may also face a greater risk.
The Columbia team said more research is needed to understand exactly how mild sleep restriction contributes to weight gain and whether improving sleep habits can reverse those effects.
“Though more research is needed to further understand how sleep restriction leads to weight gain, all of our findings suggest that insufficient sleep increases the risk of obesity-related conditions like type 2 diabetes and heart disease,” St-Onge said.
“Now we need to understand the health effects of improving sleep in those who fail to get adequate sleep on a regular basis.”
Reference:
Faris M. Zuraikat, Samantha E. Scaccia, Justin A. Cochran, Bin Cheng, Keith M. Diaz, Seth A. Creasy, Edward L. Melanson, Wei Shen, Brooke Aggarwal, Sanja Jelic, Marie-Pierre St-Onge. Prolonged Short Sleep and Its Effect on Body Weight and Composition. Annals of Internal Medicine, 2026; DOI: 10.7326/ANNALS-25-01660
Contact Newsweek editors on this story: Kara Dolman and Emma Lee-Sang
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