Losing just over an hour of sleep each night for six weeks caused measurable weight gain in adults already at risk for heart and metabolic disease, according to a study published July 7, 2026 in the Annals of Internal Medicine.
Researchers at Columbia University combined data from two clinical trials involving 95 adults ages 20 and older. All participants typically slept at least seven hours a night before the study began. Each person went through two separate six-week periods under different conditions, a design the researchers called a randomized crossover trial.
In one period, participants kept their normal sleep habits, averaging seven or more hours a night. In the other, they were told to delay their bedtime by 90 minutes, cutting their nightly sleep by about an hour and a half. That worked out to an average loss of 78 minutes per night across the sleep restriction period.
The results showed that participants who slept less gained almost one pound over the six weeks. That may sound small, but the researchers also found changes in body composition and behavior that went beyond the number on the scale.
To track sleep, participants wore wrist devices called actigraphs, which measured movement and estimated sleep duration. They also kept sleep diaries, and the research team reviewed those regularly to keep participants on schedule. Before and after each six-week period, researchers took a range of measurements. Those included body weight, waist circumference, and magnetic resonance imaging scans to assess fat and muscle volume.
Blood samples were collected to measure hormones tied to hunger and energy balance. Leptin and ghrelin, two hormones that play a role in appetite regulation, were among those tested. The same wrist devices used to track sleep also recorded daily activity levels, letting researchers compare how much participants moved under each sleep condition.
For a smaller group within the study, total daily energy expenditure was measured using a method called doubly labeled water, which tracks how the body burns calories over time.
Participants who slept less were also found to be more sedentary during their restricted sleep periods. The combination of more time awake, less physical activity, and shifts in hunger hormones points to a pattern that could contribute to gradual weight gain over time, according to the study's authors.
The researchers noted that their findings apply specifically to adults who were already considered at elevated risk for heart and metabolic problems. That group may be particularly sensitive to the effects of sleep loss. The study's authors said the results point to sleep as an important part of weight management strategies, especially for people managing cardiovascular or metabolic risk factors.
The study adds to a growing body of research connecting sleep habits to physical health outcomes beyond fatigue and mood. Prior research has linked sleep deprivation to changes in appetite hormones, increased calorie intake, and reduced motivation to exercise, all of which can contribute to weight gain over time.
The findings were published by the journal Annals of Internal Medicine on July 7, 2026, and were reported by Healthline.
