A night without sleep and ghrelin: a study of nine men

A study from the University of Lübeck (Journal of Sleep Research, 2008): the same nine healthy normal-weight men spent three nights in the sleep laboratory, one with 7 hours of sleep, one with 4.5 hours and one with no sleep. After the night without sleep, circulating ghrelin was 22% higher than after the 7-hour night, and self-reported hunger was stronger. Morning leptin did not change.

The speed of the effect: one night is enough

One night without sleep produced a measurable hormonal effect. After the 4.5-hour night, ghrelin was at an intermediate level.

The study does not say what happens to people who sleep five or six hours for many nights in a row: it observed one night at a time, in nine people.

An evolutionary explanation, which this study does not test, is that reduced sleep went with danger.

On this hypothesis, the brain responds by raising hunger to compensate, and ghrelin drives food-seeking: useful when food was scarce, less so now that it is always within reach.

Leptin and ghrelin: the dual appetite control system

Ghrelin pushes towards hunger, leptin towards satiety. In this study, after a night without sleep, ghrelin rose while morning leptin stayed the same. An earlier study, with two nights of 4 hours, had also seen leptin fall.

The authors conclude that sleep loss disturbs the hormonal regulation of energy and, in the long run, may favour weight gain: a hypothesis, not an outcome measured here.

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 measure ghrelin, it does not calculate hunger indices and it does not diagnose: this research describes groups of people, not you. These are data to read together with your doctor.