A Columbia University clinical trial published in Annals of Internal Medicine in July 2026 found that adults who slept about 80 minutes less per night for six weeks gained roughly a pound. The extra weight was driven not by hunger, but by more time spent sitting.
Researchers pooled data from two randomized trials involving 95 adults aged 20 or older who normally slept at least seven hours a night. All were at elevated cardiometabolic risk, meaning they carried a raised chance of heart disease or type 2 diabetes.
In one six-week phase, participants delayed their bedtime by 90 minutes. In the other, they kept to their usual schedule. Wrist devices tracked sleep and daily activity throughout.
The extra weight came from moving less
During the short-sleep phase, body weight rose by about 0.45 kilograms, roughly one pound, and waist circumference expanded by around half a centimeter. Sedentary time increased by an average of 17 minutes per day, and by nearly 30 minutes for men and postmenopausal women.
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Notably, leptin, the hormone that signals fullness, actually rose during short sleep rather than fell. The pattern pointed to inactivity, not appetite, as the driver of the weight gain.
"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," said Faris Zuraikat, assistant professor of nutritional medicine at Columbia University Irving Medical Center.
A small number with bigger implications
One pound over six weeks looks modest on its own. The researchers argue the picture changes when the habit stretches out.
"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," Zuraikat said.
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Marie-Pierre St-Onge, professor of nutritional medicine at Columbia and the study's senior author, framed the finding in broader terms. "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.
What to make of it
The trial was small, with just 95 volunteers, and every participant already carried elevated cardiometabolic risk. Whether healthier adults would respond the same way still needs to be tested, and the authors said more research is needed to understand how sleep loss changes behavior in a way that adds weight.
Still, the takeaway offers a simple shift in emphasis. Adequate sleep may help weight management not only by tempering appetite, but by keeping people active during their waking hours. Readers with ongoing weight or metabolic concerns should discuss them with a doctor, since sleep is one factor among several that shapes long-term health.
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