Along with diet and physical activity, sleep is often presented as the third pillar of health. At night, the body rests, repairs itself, and secretes hormones essential to its proper functioning.
Adequate sleep supports immunity, concentration, mood, and muscle recovery. Conversely, nights that are too short or of poor quality make you more vulnerable to stress and promote irritability, anxiety, and difficulty concentrating.
But what do we mean by “enough”? In adults, it is generally recommended to get between 7 and 9 hours of sleep per night.
Here I explain the links between sleep and weight gain and give you my tips for stabilizing them.
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How can lack of sleep make you gain weight?
Dysregulated hunger hormones
During the night, the body regulates several hormones, including two that directly control appetite:
- leptin, secreted by adipose tissue, sends the brain a satiety signal
- ghrelin, secreted by the stomach, on the contrary stimulates the feeling of hunger.
After too-short nights, this balance gets thrown off. In a study conducted on 12 healthy young men, two 4-hour nights were compared with two 10-hour nights. They were enough to lower leptin by 18% and raise ghrelin by 28%.
Feeling of hunger increased by 24%, with a marked craving for sweet, salty, and starchy foods.
Cortisol and blood sugar
Sleep deprivation is also accompanied by a rise in cortisol, the stress hormone, at the end of the day. Research has shown that a series of 4-hour nights reduced glucose tolerance: the body then regulates blood sugar less effectively after a meal.
In the long term, these imbalances could promote fat storage. However, studies still do not allow us to say this with certainty.
Sleeping less leads to eating more
Beyond hormones, lack of sleep could directly alter eating behaviors. According to a meta-analysis, people with sleep restriction consume on average about 385 more calories per day. Their energy expenditure, on the other hand, does not change significantly.
The brain has something to do with it. A brain imaging study suggests that after shortened nights, the areas linked to reward respond more strongly to fatty and sugary foods. We give in more easily, even without actually being hungry.
Sleep also matters when trying to lose weight. In a study conducted on overweight adults following a low-calorie diet for two weeks, those who slept 8 hours 30 minutes lost significantly more body fat and less muscle mass than those who slept 5 hours 30 minutes. The number of calories lost was the same, however.
When being overweight disrupts sleep
Snoring and sleep apnea
The link between sleep and weight works both ways: excess weight can in turn impair the quality of sleep at night.
According to the French National Authority for Health, overweight and obesity are among the main risk factors for OSAHS (obstructive sleep apnea-hypopnea syndrome).
Overweight, and especially the buildup of fat in the neck and throat area, can narrow the upper airway during the night. The resulting apneas fragment sleep and prevent you from reaching the most restorative stages. The result: you wake up tired, even after a full night’s sleep.
Even a moderate amount of weight loss can improve these symptoms. If you have significant snoring, breathing pauses noticed by those around you, or daytime sleepiness, it is important to talk to your doctor. OSAHS can be diagnosed and treated.
Chronic insomnia and weight
Chronic insomnia is diagnosed when difficulty falling asleep or staying asleep occurs at least three nights a week for more than three months. It is estimated to affect about 13% of adults in France.
A long-standing sleep debt keeps the body in a state of near-constant alertness, disrupting appetite and metabolism rhythms. A vicious cycle can then set in: lack of sleep promotes weight gain, and excess weight in turn affects sleep quality.
Sleep better to better regulate your weight: my advice
Good news: you can act on this cycle through diet!
Have a light dinner, and not too late. I recommend having your evening meal at least two hours before bedtime and avoiding large, late dinners, which make digestion and falling asleep more difficult.
Think about tryptophan. This amino acid contributes to the synthesis of serotonin, which is itself a precursor to melatonin, the hormone that signals to the body that it is time to sleep. It is found in eggs, dairy products, turkey, nuts, seeds, and, in smaller amounts, bananas. Including it in dinner can be a good habit, even though its direct effect on sleep remains little studied.
Plan ahead for cravings after a bad night. The day after a short night, I recommend planning fiber- and protein-rich snacks that keep you full for longer. Plain yogurt with a handful of almonds, a piece of fruit and a piece of cheese, whole-grain bread with a hard-boiled egg.
Move gently, in daylight. Walking, stretching, or biking during the day helps rebalance energy balance and better feel tired in the evening. Exposure to natural light also helps set the body clock.
Cutting back on screens in the evening. Screen light and especially stimulating content (social media, series, emails) delay falling asleep. Putting them away an hour before bedtime is a simple and effective habit.
Sources and scientific studies
Santé publique France – Sleep: average time over 24 hours and insomnia complaint, December 2025
Karine Spiegel, Esra Tasali, Plamen Penev, Eve Van Cauter, Brief communication: Sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite, Annals of Internal Medicine, 2004
H K Al Khatib, S V Harding, J Darzi, G K Pot, The effects of partial sleep deprivation on energy balance: a systematic review and meta-analysis, Eur J Clin Nutr, 2017
M-P St-Onge, S Wolfe, M Sy, A Shechter, J Hirsch, Sleep restriction increases the neuronal response to unhealthy food in normal-weight individuals, International Journal of Obesity, 2014
Arlet V Nedeltcheva, Jennifer M Kilkus, Jacqueline Imperial, Dale A Schoeller, Plamen D Penev, Insufficient sleep undermines dietary efforts to reduce adiposity, Annals of Internal Medicine, 2010
NutriNet-Santé team – Sleep and nutrition. French National Institute of Sleep and Vigilance survey, 2016
