Restricted sleep and snacks: a study of 19 men

A randomised crossover study from the University of Chicago, published in Obesity (2016) and available on PMC (NIH), compared 19 healthy, lean young men after four nights of normal sleep (8.5 hours in bed) and after four nights of restricted sleep (4.5 hours in bed). Afterwards they had unrestricted access to an ad libitum buffet and a snack bar.

Sleep restriction was associated with +328 ± 140 kcal in snack calories (p = 0.03), mainly carbohydrates (p = 0.02).

The ad libitum buffet: measuring real behaviour

Instead of self-reporting (subject to bias), participants are offered a food selection and the food is weighed before and after. It is real eating behaviour, not declared.

Not larger meals: calories at the lunch and dinner buffets did not change, and the difference came mostly from sweet and salty snacks. Ghrelin was higher after short sleep, and the rise in evening ghrelin went with more calories from sweets (r = 0.48, p = 0.04). Leptin did not change.

The mechanism: ghrelin and the reward system

According to the authors, ghrelin can activate both hunger and reward pathways; the study was not designed to tell them apart. They cite neuroimaging studies that found changes in reward-related brain regions in sleep-deprived people.

What the study does not say

The study lasted a few days and measured a single period of unrestricted eating: the authors write that it is unknown whether the result holds for restricted sleep repeated over a longer time. It applies to 19 healthy, lean young men, not to everyone.

The Digital Twin lines up the data your devices write to your phone, such as steps, heart rate and sleep, and shows you how they change over time. It does not count calories and it does not diagnose: this research describes groups of people, not you. These are data to read together with your doctor.