Most of us shave an hour off bedtime now and then to finish a show, catch up on messages, or squeeze a little more out of the day.
A Columbia University trial published in the Annals of Internal Medicine in July 2026 found that losing about 80 minutes of sleep a night for six weeks was enough to produce a measurable weight gain.
The 95 adults in the pooled analysis delayed bedtime by 90 minutes each night and put on roughly one pound, or just under half a kilo.
The food side stayed flat. People did not eat measurably more, and leptin, the hormone that signals fullness, actually rose. The weight gain came from moving less.
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Sedentary time grew by about 17 minutes a day on average. Men and postmenopausal women spent close to 30 extra minutes a day sitting still.
Over a full year, that mild sleep loss could add up to a clinically meaningful change on the scale, according to lead author Faris Zuraikat, assistant professor of nutritional medicine at Columbia.
The sleep cut was mild. Participants still logged around six hours a night. They were not pulling all-nighters; they were doing what plenty of adults do during a busy week.
The sleep sweet spot
A separate Columbia-led analysis of about 500,000 UK Biobank participants, published in Nature on May 13, 2026, tackled the other end of the question. How much sleep keeps the body aging slowly?
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The team used blood proteins, metabolic data, and imaging to build 23 biological aging clocks across 17 organ systems. The sweet spot sat between 6.4 and 7.8 hours a night.
People who slept less than six hours or more than eight showed accelerated aging in the brain, heart, lungs, and immune system. Short sleep tracked with higher rates of depression, anxiety, obesity, type 2 diabetes, and high blood pressure.
Longer sleep lined up with respiratory and digestive problems.
Sleep duration is deeply embedded in the body's physiology and shapes organ health across a connected brain-body network. That is according to study leader Junhao Wen, assistant professor of radiology at Columbia.
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What this means for a normal weeknight
The two studies land in the same place. Dropping to around six hours is enough to shift movement and body weight within weeks. Pushing past eight carries its own cost at the organ level.
The practical window is narrow. Aim to stay inside roughly 6.5 to 8 hours on an ordinary weeknight, and treat the hour you were going to shave off as part of the day's movement budget rather than free time.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.