A modest reduction in nightly sleep can lead to measurable weight gain over just weeks, according to new research from Columbia University that challenges the assumption that only extreme sleep deprivation affects metabolism.
Researchers examined 95 adults who normally slept seven to eight hours per night. Over a six-week period, participants delayed their bedtime by 90 minutes while wearing wrist monitors that tracked sleep and activity. The result was striking in its simplicity: they gained an average of one pound and spent significantly more time sitting.
The study, published in Annals of Internal Medicine, focused on what researchers call chronic mild sleep loss, a pattern affecting roughly 30 percent of American adults who get five or six hours nightly. Previous obesity research had concentrated almost exclusively on severe deprivation, restricting subjects to four hours or less, which is difficult to sustain.
"Our study shows that getting adequate sleep may help reduce the risk of weight gain and obesity-related conditions like heart disease and diabetes," said Marie-Pierre St-Onge, the study's lead researcher and a professor of nutritional medicine at Columbia. "Focusing on eating a healthier diet and getting more physical activity to offset weight gain is simplistic and can be difficult to maintain."
The inactivity finding proved particularly telling. Participants became sedentary for an additional 17 minutes daily during the sleep restriction phase. Among men and postmenopausal women, sedentary time jumped nearly 30 minutes per day, even accounting for extra time spent awake.
"This is notable, as people who are more sedentary have elevated risk for chronic diseases," said Faris Zuraikat, the study's first author. "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."
While one pound over six weeks may seem modest, the implications scale dramatically. If extrapolated to a full year, losing roughly 80 minutes of sleep nightly could produce clinically significant weight gain, Zuraikat noted.
Earlier Work Points to Broader Metabolic Damage
The same research group previously examined this population in related studies that uncovered deeper problems. Women with elevated cardiometabolic risk who reduced sleep by 80 minutes for six weeks developed greater insulin resistance, a major risk factor for type 2 diabetes, with especially pronounced effects in postmenopausal women.
In another experiment, men and women with elevated heart disease risk showed an influx of inflammatory cells in the heart after 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 said. The team's next goal is understanding whether improving sleep in chronically sleep-deprived people can reverse these effects.
The research was funded by the American Heart Association and the National Institutes of Health.
Author Jessica Williams: "This study demolishes the myth that small sleep cuts don't matter, especially for the millions of Americans already running a sleep deficit."
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