Even modest sleep loss may quietly lead to weight gain and raise the risk of chronic disease over time.

People who reduced their nightly sleep by about 80 minutes for six weeks gained an average of one pound and spent more time being sedentary, according to researchers at Columbia University Vagelos College of Physicians and Surgeons.

“Our study shows that getting adequate sleep may help reduce the risk of weight gain and obesity-related conditions like heart disease and diabetes,” says Marie-Pierre St-Onge, a professor of nutritional medicine in Columbia’s Department of Medicine and Institute for Human Nutrition and study leader. “People tend to gain weight over the course of their adulthood, and obesity is a major risk factor for heart disease. But focusing on eating a healthier diet and getting more physical activity to offset weight gain is simplistic and can be difficult to maintain.”

Testing Realistic, Long-Term Sleep Loss

Much of the existing evidence connecting insufficient sleep with obesity comes from small, short-term studies in which participants experienced extreme sleep restriction (usually 4 hours of sleep opportunity). Those experiments have shown that severe sleep deprivation can alter appetite and encourage overeating, potentially contributing to weight gain over time.

However, most people cannot sustain such an extreme lack of sleep for more than a few days.

“These studies only show us what happens under the most extreme conditions and don’t tell us if mildly sleep-deprived people, like a lot of Americans who get 5 or 6 hours of sleep a night, will gain weight,” St-Onge says.

Six Weeks of Shorter Sleep Led to Weight Gain

To examine the effects of chronic but moderate sleep loss, a pattern followed by roughly 30% of adults, St-Onge and her colleagues recruited 95 adults who typically slept for 7 to 8 hours each night.

During one six-week phase, participants were asked to delay their usual bedtime by 90 minutes. During a separate six-week phase, they maintained their normal sleep schedule.

The researchers used wrist monitors to track sleep and physical activity during both phases. They also measured body weight, waist circumference, body composition, and fasting levels of several hormones that either stimulate or suppress appetite.

“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,” says Faris Zuraikat, assistant professor of nutritional medicine in Columbia’s Department of Medicine and Institute for Human Nutrition and first author of the study. “Our study was designed to mimic sleep patterns that most adults experience chronically. When extrapolated to a full year, we would expect that losing less than an hour and a half of sleep per night could result in clinically meaningful weight gain.”

Less Sleep Also Meant More Inactivity

During the restricted-sleep phase, participants spent an average of 17 additional minutes per day being sedentary. Among men and postmenopausal women, sedentary time increased by nearly 30 minutes per day.

“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,” Zuraikat says. “This is notable, as people who are more sedentary have elevated risk for chronic diseases.”

Sleep Loss May Affect Metabolic and Heart Health

The researchers are still working to determine exactly why moderate sleep restriction contributes to weight gain.

In a previous related study involving a subset of the same participants, St-Onge’s team reported(link is external and opens in a new window) that women with elevated cardiometabolic risk developed greater insulin resistance after reducing their sleep by about 80 minutes per night for six weeks. Insulin resistance is a risk factor for type 2 diabetes, and the effects were stronger among postmenopausal women.

In another study of the same group, St-Onge found that mild sleep restriction caused an influx of inflammatory cells in the hearts of men and women who already had an elevated risk of heart disease.

“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 says.

“Now we need to understand the health effects of improving sleep in those who fail to get adequate sleep on a regular basis.”