Sleep (and nutrition)

Sleep is not a simple “pause” but an active process of repair, memory consolidation, hormonal regulation and brain cleansing. It interacts deeply with nutrition in both directions.

Sleep drives appetite: a powerful and underestimated link, as lack of sleep directly disrupts appetite hormones

1. It lowers leptin (satiety) and raises ghrelin (hunger), so you are hungrier after a bad night
2. It increases the craving for fatty and sugary foods (the tired brain looks for quick rewards and easy energy)
3. It impairs insulin sensitivity, so a single short night is enough to temporarily worsen glucose tolerance
4. It raises cortisol (stress, fat storage)

The result: sleeping little encourages overeating and weight gain, regardless of willpower. Sleep is a neglected pillar of weight management, often more decisive than people think. You can “sabotage” a perfect diet with poor sleep.

The reverse: food influences sleep. What you eat (and when) affects sleep quality:

1. Caffeine: its long half-life (5 to 6 hours) disrupts deep sleep even when drunk in the afternoon (see caffeine, adenosine)
2. Alcohol: makes you drop off but worsens quality (less REM sleep, waking in the night)
3. Heavy or late meals: disturb falling asleep and sleep itself (digestion, reflux, blood sugar)
4. Tryptophan plus carbohydrate in the evening: favour serotonin and melatonin (see tryptophan)
5. Magnesium: supports relaxation and sleep
6. Fast sugars and blood sugar spikes: overnight fluctuations in blood sugar can cause waking

Brain cleansing (the glymphatic system): a fascinating discovery, as during deep sleep the brain activates a “cleaning” system (the glymphatic system) that clears accumulated metabolic waste (including proteins linked to Alzheimer’s, such as beta-amyloid). Good quality sleep is therefore protective for the brain in the long term.

In practice (sleep hygiene plus nutrition):

1. Coffee in the morning or at lunchtime only; avoid it in the afternoon
2. Eat dinner early and light; avoid alcohol in the evening
3. A source of tryptophan plus complex carbohydrate in the evening if needed
4. Keep regular times (the body clock likes consistency)
5. Natural light in the morning, darkness in the evening (melatonin)
6. Treat sleep as a health priority on a par with diet and activity