Losing 80 Minutes of Sleep a Night Made People Gain Weight, and Not by Eating More
You do not have to pull all nighters to work against your waistline. A new Columbia study found that losing just 80 minutes of sleep a night pushed weight up over six weeks. The interesting part is why: not that tired people ate more, but that they quietly moved less.
What the Study Found
Led by Columbia nutrition professor Marie-Pierre St-Onge and published in Annals of Internal Medicine, it had 95 adults who normally slept seven to eight hours. Each spent six weeks sleeping normally and six staying up 90 minutes later, roughly 80 fewer minutes a night. After the short phase they gained about a pound, their waist grew half a centimeter, and body volume rose slightly. Most sleep research used severe deprivation nobody sustains; this tested the everyday shortfall a third of adults live with. A pound over six weeks sounds trivial, but over years, it is how adult weight creep adds up.
The Surprise: You Move Less, Not More
Being awake longer should mean more movement and calories burned. The opposite happened. On short sleep, participants grew more sedentary, adding about 17 minutes of inactivity a day, nearly 30 among men and postmenopausal women, even accounting for the waking hours. And unlike the extreme studies, where appetite hormones drive overeating, here those hormones barely budged. The driver was behavioral: mild sleep loss drains the energy behind incidental fidgeting and pacing that quietly burns calories. Tired people do not compensate; they sink into the couch.
It's Not Just Weight
In related work on the same group, mild sleep restriction raised insulin resistance, a precursor to type 2 diabetes, worst in postmenopausal women, and drew inflammatory cells into the heart. Sleep is active maintenance, and cutting it short reaches well beyond the scale.
What to Do
Aim for the seven to nine hours most adults need, and treat it like a workout or a meal. Keep sleep and wake times consistent, build a wind down routine, and cut late light, screens, caffeine, and alcohol, in a dark, cool bedroom. If you cannot add hours, stop sabotaging the ones you get.
The Bottom Line
The finding reframes the eat better, move more advice St-Onge calls simplistic: sleep belongs beside diet and exercise. It is not the reward you collect after the real work; it is part of it. If your diet and training are not adding up, the missing variable might be the hour of sleep you keep giving away.
This article is educational and is not medical or dietary advice. Sleep needs vary by individual. If you have persistent sleep problems or concerns about your weight or metabolic health, talk to a doctor or a qualified professional.
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This story was originally published July 14, 2026 at 1:31 PM.