The findings add to growing evidence that consistently getting enough sleep may play an important role in preventing weight gain and lowering the risk of obesity related diseases.

“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.”

Looking Beyond Extreme Sleep Deprivation

Much of the previous research connecting poor sleep with obesity has focused on severe sleep deprivation, often limiting people to only four hours of sleep. Those studies have shown that extreme sleep loss can increase appetite and overeating, factors that contribute to weight gain.

However, such severe sleep restriction is difficult for most people to tolerate 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.

To better reflect real life, the researchers examined the effects of chronic, mild sleep loss, a pattern experienced by roughly 30% of adults.

Six Weeks of Less Sleep Led to Measurable Changes

The study included 95 adults who normally slept between 7 and 8 hours each night. During one six week study period, participants delayed their usual bedtime by 90 minutes. During another six week period, they followed their normal sleep schedule.

Throughout both phases, participants wore wrist monitors that tracked sleep and physical activity. Researchers also measured body weight, waist circumference, body composition, and fasting levels of several hormones involved in appetite regulation.

“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 Sitting

The researchers found that participants became less active during the sleep restriction phase. On average, sedentary time increased by 17 minutes per day. Among men and postmenopausal women, inactivity rose by nearly 30 minutes each 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.”

Earlier Research Suggests Broader Health Effects

The same group of participants has also been examined in related studies. In one previous investigation, women with increased cardiometabolic risk who reduced their sleep by about 80 minutes each night for six weeks developed greater insulin resistance, an important risk factor for type 2 diabetes. The effect was especially pronounced in postmenopausal women.

Another study found that men and women with elevated heart disease risk developed an influx of inflammatory cells in the heart after experiencing mild sleep restriction.

“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.”

The study, titled “Skimping on Sleep and Its Impact on Body Weight and Composition: A Pooled Analysis of Randomized Trials,” was published on July 6 in Annals of Internal Medicine.

The authors are Faris Zuraikat, Samantha Scaccia, Justin Cochran, Bin Cheng, Keith Diaz, Seth Creasy (University of Colorado), Brooke Aggarwal, Sanja Jelic, and Marie-Pierre St-Onge.

The authors report no conflicts of interest.

The research was supported by the American Heart Association (16SFRN27950012) and the National Institutes of Health (R01 HL128226, UL1 TR001873, P30 DK026687, R01 HL173190, R01 HL155190, R01 HL153642, K01 HL145023, R01 HL169991, R01 HL106041, R35 HL155670, R01 AG071032, R56 DK136601, P30 DK048520, and R01 DK128154).