People who slept 1.2 hours more a day ate 270 kcal less.
Nobody told them to change what they ate.
Eighty people, and the only change was sleep
A 2022 University of Chicago study took 80 adults with overweight who normally slept under 6.5 hours and split them into two groups.
One group got a single sleep counseling session, and the researchers watched for two weeks. No instructions about food.
| After two weeks | Sleep extension group | Control group |
|---|---|---|
| Sleep duration | +1.2 hours | No change |
| Daily calorie intake | −270 kcal | Baseline |
| Total energy expenditure | No difference | No difference |
Intake was measured with doubly labeled water. It is calculated from the water leaving the body rather than from a food diary, so under-reporting cannot creep in.
Hold 270 kcal for a year
270 kcal a day is 98,550 kcal in a year, worth 12.8 kg of body fat.
The body adapts, so you would not lose all of it. The direction is not in doubt.
Short sleep raises hunger hormones
- •Ghrelin (hunger) rises: you get hungry more often
- •Leptin (fullness) falls: the full signal arrives late
- •Prefrontal activity drops: holding back gets harder
- •The reward circuit sharpens: sweet and greasy food looks better
All four fire at once, which is why bread has such a pull the day after an all-nighter.
One session added 1.2 hours
The study ran one personalized sleep hygiene session and nothing else. No drugs, no devices.
It was the usual advice: less screen time before bed, a fixed time to get into bed.
Fix your wake-up time first. Bedtime follows. Doing it the other way around usually fails.
Lying down 30 minutes earlier is easier than 30 minutes on a treadmill
Thirty minutes of running burns about 300 kcal. An extra 1.2 hours of sleep keeps 270 kcal out.
The sizes are close. One is hard to do every day and the other is lying down.
Sources · Tasali et al., JAMA Internal Medicine (2022) · US National Institutes of Health research summary · literature on sleep and appetite hormones