Losing 80 minutes of sleep a night led to weight gain in a trial

Short sleepers tend to weigh a little more than sound sleepers, a link that turns up across large population surveys. What those surveys can never settle is the direction: does losing sleep push weight up, or does the extra weight wreck the sleep?

To settle it, researchers at Columbia University ran an experiment instead of another survey. Their results, published in the journal Annals of Internal Medicine, come from 95 healthy adults who normally slept seven to eight hours a night.

For six weeks they gave up about 80 minutes of sleep a night, a little under an hour and a half, with each person also completing six weeks of normal rest for comparison. On the shorter schedule they gained about one pound, and the extra weight traced to time spent sitting still.

A sleep debt, on purpose

The way the experiment was built is what makes it hard to dismiss. Each volunteer went through six weeks of sleep restriction and, after a break, six weeks of adequate sleep, so their short nights were judged against their own well-rested ones.

Because each person served as their own comparison, the usual objection to sleep studies, that heavier people simply sleep worse, does not apply here. That design is why the authors can write that moderately short sleep may lead to weight gain, a cause-and-effect claim a one-time snapshot could never support.

What sets this apart is how ordinary the sleep loss was. Earlier experiments mostly pushed people into severe, short-term sleep deprivation; this one asked healthy adults to lose less than an hour and a half a night, the sort of shortfall a busy week routinely delivers.

Extra hours on the couch

When the volunteers slept less, they also moved less. Their sedentary time, the waking hours spent sitting or lying still, rose by about 17 minutes a day. The slowdown was larger in some groups: among men and postmenopausal women, sitting time climbed by nearly 30 minutes each day.

The pattern survived an obvious challenge. Shorter nights leave people awake longer, with more time on their feet, yet they still ended up more sedentary. As Faris Zuraikat, the study’s first author, put it, participants “spent more time being inactive than when they got adequate sleep”.

That points to a quieter route to weight gain. Trim a night’s sleep, and the body drifts toward moving less rather than toward bigger meals.

One pound, in perspective

A pound is not a dramatic number, and the researchers are the first to say so. Zuraikat called the one-pound gain “not overwhelming,” while stressing that it built up over just six weeks.

The people involved were also a particular group. All were 20 years or older and already carried a raised risk of heart and metabolic disease, so the same six weeks might move the numbers differently in someone younger or healthier. The authors add their own cautions: the window may have been too short to capture deeper changes in body composition, and the effect sizes were modest.

The finding does not land in a vacuum. Short sleep has been tied to body weight for years, and federal health guidance already lists obesity among the problems that sleep deficiency is linked to, alongside heart disease and diabetes. What this trial adds is direct evidence on the causal effect on weight of milder, everyday sleep loss, a question earlier studies had left open.

Where this leaves you

For anyone trying to keep their weight steady, the useful takeaway is that sleep belongs alongside diet and exercise. St-Onge points out that relying on food and exercise alone to offset weight gain is “simplistic and can be difficult to maintain,” and that guarding sleep may ease some of that burden.

For now the honest read is modest: protecting your sleep is a low-risk way to keep a little extra weight from creeping on.