How even a couple bad nights shift your hunger hormones toward overeating.
What the evidence says
- Ghrelin (hunger hormone) increases 28% with sleep restriction — *under `csh03`'s controlled protocol: 12 healthy young men, 2 days at 4 hours, with caloric intake and activity held constant. Under free intake a longer study found the hormones reading the opposite way while people overate anyway; see `ksh04`, which holds both and reconciles them*[1]
- Leptin (satiety hormone) decreases 18% with sleep restriction[1]
- Hunger ratings rose 24% and appetite ratings 23%. The study stopped there: it measured ratings, not eating. This bullet read "= overconsumption" until 2026-09-02 — `csh03` fixed caloric intake by design, so nobody in it could overconsume, and it measured no intake, no expenditure and no weight[1]
- Changes occur within just 2 nights of restricted sleep (4h vs 10h), in a crossover trial of 12 healthy young men[1]
- The shift is food-specific: appetite for calorie-dense, high-carbohydrate foods rose 33-45%, while appetite for fruits, vegetables and high-protein foods was not significantly affected[1]
- *The authors' own stated limitation, held for the first time on 2026-09-02 and carried by no file until now: "The study included only 12 young men and did not measure energy expenditure." So `csh03` cannot speak to energy balance. It measured hormones and subjective ratings of hunger and appetite — not intake, not expenditure, not weight. A page may say sleep restriction shifted appetite hormones and self-reported hunger in these twelve men. It may not say sleep loss makes people gain weight on this citation*[1]