Small sleep declines drove weight gain in at-risk adults

Clinical takeaway: Ask about sleep duration when counseling patients on weight and cardiometabolic risk. Even a modest, sustained shortfall may contribute to gradual weight gain.

The advice to protect sleep for weight control has rested on shaky causal ground, drawn from either correlational studies or brief experiments imposing severe deprivation. Neither tells a clinician whether the garden-variety shorter sleep that patients typically report, an hour or so under what they need, carries real metabolic cost. This randomized crossover trial tested that everyday shift directly.

Over six weeks of sleep restriction of about 78 minutes less per night, participants gained about 0.5 kg, roughly one pound, compared with their adequate-sleep phase, with body weight rising to 71.6 kg (157.8 lb) from 71.1 kg (156.7 lb). Waist circumference grew by about half a centimeter, and whole-body volume on MRI rose modestly.

Sedentary time rose by about 17 minutes a day during the short-sleep phase, even after accounting for the extra waking hours, while moderate-to-vigorous activity held steady. Fasting leptin edged up in line with the added weight, but ghrelin and GLP-1 barely moved, and total daily energy expenditure was unchanged.

The pooled analysis combined two randomized crossover trials that enrolled a combined 95 adults aged 20 years or older with elevated cardiometabolic risk who habitually slept at least seven hours. Each completed a six-week adequate-sleep phase and a six-week phase with bedtime delayed to trim sleep, separated by a washout. Adiposity was measured by MRI and activity by wrist actigraphy.

The mechanism looks more behavioral than hormonal. Research on severe restriction tends to attribute sleep-related weight gain to dysregulation of appetite hormones leading to overeating, but with this milder reduction that was not the case. What moved instead was the time spent sedentary, suggesting the extra weight tracks with reduced movement rather than a hunger surge. That matters for how clinicians frame it: encouraging tired patients to stay active may do more than warning them against snacking.

"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," he concluded.

Source: Zuraikat FM, et al. (2026 Jul 7) Ann Intern Med. Prolonged Short Sleep and Its Effect on Body Weight and Composition: A Pooled Analysis of Randomized Trials