You know the feeling.
You barely slept the night before, spend the day struggling to stay awake, and suddenly the biscuits, fried food or chocolate in the kitchen look much more tempting than usual.
It is easy to blame yourself for having “no willpower”.
But science suggests that being tired can actually change the way your body and brain respond to food.
Your hunger signals can change
Sleep and appetite are closely connected.
Research has linked insufficient sleep with changes in hormones involved in hunger and fullness. Ghrelin, often described as a hunger-promoting hormone, can increase, while leptin, which helps signal that you have had enough to eat, can decrease under some sleep-loss conditions.
That does not mean one bad night automatically makes you overeat.
But repeated or significant sleep loss can make hunger and food choices harder to manage.
A 2025 review of research on sleep and eating behaviour found that sleep duration, quality and timing can all influence energy intake, food choices and when people eat.
And suddenly, junk food looks better
There may be more going on than simply feeling hungry.
Sleep deprivation can also affect the brain’s reward systems, making high-calorie foods more appealing. Research has found that people who are sleep-restricted can consume more calories, with some studies reporting increases of hundreds of calories a day.
That helps explain the familiar late-night situation.
You are tired. You want something quick. A bowl of vegetables does not seem nearly as exciting as a plate of fries.
Your brain may simply be looking for an immediate source of energy and reward.
It is not just about weight
The relationship between sleep and eating is important for more than appearance.
Poor sleep is associated with a range of health problems, and researchers are increasingly studying sleep as part of the bigger picture of metabolic health.
The National Institutes of Health notes that laboratory studies have found sleep restriction can stimulate appetite and increase cravings for high-calorie foods.
More recent research continues to examine how sleep, eating patterns and metabolic health interact rather than treating them as completely separate issues.
So what can you do?
The answer is surprisingly simple: take sleep seriously.
If you are constantly tired, relying on snacks to stay awake may be treating the symptom rather than the problem.
Getting enough sleep will not magically create a perfect diet, and people respond differently to sleep loss. But consistently getting adequate, good-quality sleep can be one useful part of maintaining healthy eating habits.
So the next time you find yourself standing in the kitchen late at night wondering why you suddenly want everything in sight, remember:
You may not simply be hungry. You may be tired.
Sources: National Institutes of Health, Frontiers in Psychiatry, Scientific Reports, Cambridge University.
