Adults who shortened their sleep by an average of 80 minutes per night gained roughly half a kilogram over six weeks and spent more time sedentary, according to a real-world study conducted by researchers at Columbia University. The trial, which tracked 95 participants over the age of 20 in their home environments, compared a period of normal seven-to-nine-hour sleep with a period in which bedtimes were delayed, cutting sleep by about 90 minutes. The resulting sleep loss was linked not only to weight gain but also to a measurable drop in physical activity.

The mechanisms behind the weight increase are multiple, the researchers note. Sleep deprivation disrupts hormones that regulate appetite, heightens cravings for calorie-dense and sugary foods, and raises levels of the stress hormone cortisol. At the same time, chronic low-grade inflammation rises, and the drop in energy reduces the inclination to exercise. If the pattern persists for months or years, the researchers warn, it could lead to substantial weight accumulation.

The findings add to a growing body of evidence on the broad health consequences of poor sleep. Neurologist Conrado Estol has separately warned that shifting sleep schedules between weekdays and weekends raises the risk of depression, and cited a muscle biopsy study in sleep-deprived young people that showed a significant increase in markers of inflammation and cellular injury. Estol also noted that maintaining consistent sleep schedules, even on weekends, is associated with a lower risk of death from any cause, including cancer and cardiovascular disease. Other research indicates that regularly staying up late can weaken immune function and further disrupt the hormones governing hunger and satiety.

The Columbia study underscores that even modest, sustained sleep restriction—well within the range common in modern lifestyles—can produce tangible metabolic changes within weeks. While the trial did not prescribe a specific intervention, its authors and other specialists stress that consistent sleep of seven to nine hours per night should be considered a pillar of weight control and overall health.