Sleeping 80 minutes less for six weeks: about a pound heavier and more time sitting

Nobody much minds going to bed late once in a while. But if you slept more than an hour less every night for six weeks in a row, what would happen to your body?

A team at the Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, gives specific figures in one study. After six weeks of sleeping about 78 minutes less per night on average, participants gained 0.45 kg (about 1 lb) in weight on average, had a waist 0.52 cm larger on average, and spent about 17 more minutes a day sedentary on average.

The research letter was published in Annals of Internal Medicine under the title "Prolonged Short Sleep and Its Effect on Body Weight and Composition". The first author is Faris M. Zuraikat, and it was published online on 7 July 2026.

The same people: first enough sleep, then less

The study is a pooled analysis of two randomised crossover trials. Each participant completed two phases: six weeks of adequate sleep and six weeks of restricted sleep, with a washout period between them. In other words, the comparison is not with other people but with the same person under two sleep conditions.

The sample was 95 adults, all aged 20 or over, who usually slept at least 7 hours a night and had elevated cardiometabolic risk.

The protocol delayed bedtime by 90 minutes. As measured, participants slept 78.4 minutes less per night on average during the restricted phase, about an hour and a half; the university press release summarises this as about 80 minutes.

A pound in weight, half a centimetre at the waist, seventeen more minutes sitting

After six weeks of restricted sleep, participants gained 0.45 kg in weight on average, and their waist circumference rose by 0.52 cm on average.

On activity, participants spent 17.2 more minutes a day sedentary on average during the restricted phase. The result still held after the researchers adjusted for differences in time in bed.

The university press release adds that sedentary time rose by nearly 30 minutes among men and postmenopausal women. However, this figure appears only in the republished press release and we could not check it against the paper itself, so it should be treated with caution.

On the other hand, no clear change in body composition, such as fat mass, was detected within the six weeks. The researchers suggest that six weeks may have been too short to detect one.

The numbers are small, and the limits come first

The findings are easily inflated into "sleeping less makes you fat", but the actual results are not that simple. Keep at least these points in mind when reading:

• The effect is modest: the researchers themselves note that the changes observed were modest.
• Only 95 people: the sample size limited subgroup analyses by sex and menopausal status.
• Only six weeks: the intervention was short, and there are no measured data on longer-term effects.
• Not the general population: participants had elevated cardiometabolic risk, so the results may not apply to other groups.
• The one-year claim is an extrapolation: the senior author says that, extrapolated from the six-week results to a full year, sleeping less than 90 minutes less per night "could result in clinically meaningful weight gain" (per the university press release). This is an extrapolation, not a measured result.
• Independent experts also urge caution: according to the Science Media Centre in Spain, experts say the findings should not be over-interpreted, can only be treated as speculative, cannot be extended directly beyond people at cardiometabolic risk, and should not support firm conclusions about cause and effect.

One further note: as of October 2026 we have not been able to read the full paper directly. The figures here come from the Medical Dialogues report, the republished university press release and the Science Media Centre España page, so they are second-hand. Details such as confidence intervals and funding sources could not be verified.

Putting sleep in the schedule: an everyday observation

What follows is a general everyday observation, not a research conclusion; the study did not test any specific routine.

On a calendar, client meetings, team meetings and follow-up calls all have fixed slots, but sleep can easily become the slot left over. Seeing one more client or editing one more document in the evening may cost you bedtime.

One simple approach is to treat bedtime as an appointment that is not easily moved, written into the calendar like any other meeting. When you schedule an evening meeting, fix its end time first rather than working it out afterwards. This is not medical advice; it just turns "how long to sleep" from an ad hoc decision into something planned in advance.

The study did not prove that sleeping less inevitably makes people gain weight, but it is a reminder: the hour or so taken from each night may not be free.

This article provides general health information only and is not a diagnosis or treatment advice. If you have concerns about your own sleep or weight, please consult a doctor or another qualified health professional.

Prices and details correct as of October 2026

This article is general health information, not medical advice. For any health concern, consult a doctor or registered health professional.