People arrive at our nutrition clinic with a food diary and a stalled scale, convinced the problem is in the diary. Quite often it is in the four hours before midnight instead.
What short sleep does to appetite
Two hormones do most of the work here. Ghrelin tells you to eat; leptin tells you to stop. A run of short nights pushes ghrelin up and leptin down, which is a fairly precise recipe for eating more without feeling like you have.
Members who log fewer than six hours a night eat, on average, around 300 more calories the following day — almost all of it after 8pm.
It also changes what you want
It is not only quantity. Tired brains reliably reach for fast carbohydrate and fat. This is not weakness — it is a tired prefrontal cortex outvoted by a reward system that is working perfectly well.
The other direction is true too
Sleep affects eating, and eating affects sleep. A very large meal within two hours of bed, alcohol, and caffeine after mid-afternoon all fragment sleep in ways you will not remember in the morning but will feel all day.
- Keep the last substantial meal about three hours clear of bed.
- Treat alcohol as a sedative, not a sleep aid — it shortens the restorative half of the night.
- Caffeine has a half-life of roughly five hours. A 4pm coffee is still half-present at 9pm.
A fortnight’s experiment
Before you change a single thing about your food, try this: hold a consistent bedtime for fourteen nights, within about half an hour either side, weekends included. Log your meals exactly as you do now. Most people find intake falls without any conscious restriction at all.
If it does not, that is genuinely useful information — and the sort of thing worth taking to a nutritionist rather than guessing at.
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