How does sleep influence weight?

[Article updated on 19/09/2023]

When it comes to losing weight or feeling better about your body, improving your diet and getting back into physical activity are the first things to do. However, they are not the only ones. Despite a balanced diet and regular physical activity, some people find that weight loss is not achieved, and we can sometimes even observe the opposite effect. It is then legitimate to ask what is the cause of this situation. Sleep can have a very important influence on weight loss (just like stress for example), so we need to take a closer look to understand why.

Before reading on

I’m not an expert in this field, but I am passionate about nutrition and health.

The articles you’ll find on my site are the result of in-depth research that I’d like to share with you. However, I would like to stress that I am not a health professional and that my advice should in no way replace that of a qualified physician. I’m here to guide you, but it’s important that you consult a professional for specific questions or medical concerns. Your well-being is important. So be sure to consult the appropriate experts and take the best possible care of yourself.

What is sleep, exactly?

Far too often neglected, especially when the days are not long enough to do everything we would like, it is nevertheless very important, especially for physical and psychological recovery.

Sleep is a succession of cycles which are divided into two phases:

  • The slow phase (light and deep slow sleep): reduction in the body’s physiological activity. He rests and recovers from the fatigue accumulated during the day.
  • The paradoxical phase (shorter – around 20% of total sleep – but much more intense than the first): decrease in muscle tone and very rapid eye movements. It is during this phase that we dream and store information from our day in memory.

Fatigue can be due to a lack of sleep (we go to bed late and get up early: we sleep well but not enough) or to sleep disorders. There are two main types:

  • Dysomnia: these disorders can affect both the quality and quantity of sleep. They are of psychological origin, due to the environment (when your companion snores for example, etc.), narcolepsy, lifestyle (consumption of alcohol, too rich a diet before sleeping, jet lag), etc.
  • Parasomnias: these are sleep disturbances but do not always have an impact on our day. This includes night terrors, sleepwalking, bruxism (teeth grinding) and even sleep apnea…

The ideal would be to have quality sleep and not find yourself in sleep debt (difference of one hour between a person’s ideal sleep time and the actual sleep time over a week).

In addition to having an impact on our energy and/or our mood, lack of sleep can impact our weight.

Chrononutrition highlights the importance of sleep

How can our sleep affect our weight?

Initially, lack of sleep will affect our desires. You’ll notice that when you’re tired, you tend to crave comfort food more. Most of the time this food is rather fatty or sweet (or both). Who has never grabbed a packet of cakes or a packet of crisps when coming home from work after a very tiring day?

Eating this food then gives you pleasure and puts aside this fatigue for a moment. It feels good and we ask for more because once sweet products are consumed, they release dopamine (“happiness hormone”) in the brain. And this is where it becomes problematic.

Occasional fatigue will not pose a problem. However, chronic fatigue will lead to an increase in the consumption of rich products on a daily and long-term basis. It’s a vicious circle.

From a biological point of view, lack of sleep leads to hormonal imbalance. Leptin is reduced (satiety hormone: it suppresses hunger) and ghrelin is increased (it, on the contrary, is at the origin of the feeling of hunger) and as seen previously this change will lead to an increase in hunger. and consumption.

So it’s not a “lack of willpower” when you reach for cookies lying around in the cupboard, it’s your body that demands these foods!

A lack of sleep can also lead to insulin resistance. This hormone secreted by the pancreas is in some way the key to opening the doors of muscle and adipose cells (fat cells) to bring in glucose and store it. In case of insulin resistance, the hormone has more difficulty regulating blood sugar (blood glucose level), which therefore leads to negative consequences. As the glucose present in the blood is no longer stored optimally, it is transformed into fatty acids in larger quantities. This transformation can lead to weight gain but above all an increase in triglycerides in the blood and a drop in HDL cholesterol (the good cholesterol). In the long term, this can lead to the onset of diabetes…

And these are some of the possible mechanisms among those that have been studied and proven.

Numerous studies have shown that poor sleep leads to an increased risk of obesity (particularly in patients with obstructive sleep apnea).

A 2010 study also showed that poor sleep would have the effect, in the case of a low-calorie diet, of reducing the loss of fat mass and increasing the loss of muscle mass. So you can eat as well as possible and get good physical activity, your body will do as it pleases if you don’t sleep well enough.


Sleep disorders are not always easy to manage, but you should remember to talk to your doctor if you notice any changes in this area because it is not trivial.

Apart from proven disorders, simple habits to put in place can improve the quality of your sleep: going to bed at set times, avoiding screens before going to bed, encouraging reading a book, managing daily stress, not do not do physical activity too close to bedtime…

Weight is very complex, it is rarely all black or all white. As said in the preamble, if despite physical activity and a balanced diet, you are unable to lose weight, it is because there are other factors that influence this. You then have to look further than your plate and address the real cause of the problem. Sleep is particularly part of this, so take care of your sleep, to take care of your body.