How Does A Lack Of Sleep Cause Weight Gain

  • Post last modified:August 11, 2021
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Does a lack of sleep make you gain weight? Unfortunately, the answer is YES.

A new study makes it clear that adults who sleep less than their peers are more likely to be overweight or obese. 

If you have insomnia or similar problems, please read on.

Let’s first look at two research data points: 

  • National Health and Nutrition Examination Survey (NHANES) shows that people who sleep less than 5 hours a night are almost twice as likely to be obese as those who sleep 7 to 9 hours.
  • A follow-up study of the lifestyle habits of 68,000 women from 1986 to 2002 found that continuous lack of sleep can cause weight gain and other health problems.

There are many related research reports and the conclusions are very consistent.

The evidence is clear that a lack of sleep can cause weight gain, whether in adults or children.[*].

There are many reasons for this result.

How Does A Lack Of Sleep Cause Weight Gain

How Does A Lack Of Sleep Cause Weight Gain

The increase or decrease in body fat is usually the result of hormonal changes or imbalances.

This is why people with hypothyroidism usually gain weight easily and have difficulty losing weight. This is also the reason that women increase body fat during pregnancy. For another example, bodybuilders undergo changes in their bodies after taking steroids.

Therefore, the hormones in our bodies have considerable power. If you want to lose weight successfully, you need to understand hormones. They not only regulate weight but also have a great impact on overall health.

In this article, we are going to discuss how a lack of sleep affects hormones and makes you gain weight.

1. Leptin and Ghrelin

  • Leptin is a hormone produced by fat cells. It will reduce your appetite.
  • Ghrelin (also known as the hunger hormone) is a hormone that increases appetite and also affects weight gain.

When you lose weight, the level of leptin (appetite suppressant) will decrease. When you gain weight, the level of leptin will be higher.

I know this sounds contradictory? If the leptin level is high, it should be able to suppress appetite better to help you lose weight. 

Dr. Mary Dallman, an obesity expert at the University of California, San Francisco, explained: “Many obese people have developed a resistance to the appetite-suppressing effects of leptin.”

One of the causes of leptin resistance is lack of sleep, or reversal of the day and night (circadian rhythm disorder). This is common in many night shift workers, such as doctors and nurses.

One study has found that when sleep is insufficient, your body will produce more ghrelin. At the same time, leptin will decrease.

In other words, lack of sleep will make you eat more.

Scientists believe that leptin levels increase as sleep time increases. Ghrelin, however, will decrease as sleep time increases.

These two hormones play a great role in helping your body regulate fat. Therefore, if you want to lose weight, you need to deal with the relationship between these two hormones.

2. Insulin 

Insulin is another hormone that plays an important role in regulating body fat. It can also be severely affected by sleep (or lack of sleep).

The job of insulin is to transport sugar in the blood to the organs and tissues and also to regulate blood sugar levels.

If you experience a problem with insulin function or insulin resistance, it can lead to a series of health problems including obesity and diabetes.

In addition to unhealthy eating habits, lack of sleep can also cause insulin resistance.

Now we know how harmful hormonal disorders are to the body.

  • An increase in ghrelin will make you feel hungry in the morning and make you want to eat in the middle of the night when you cannot sleep.
  • Additionally, insulin resistance keeps your blood sugar at a high level. The sugar in your body cannot be completely metabolized. It is then converted into fat and continuously stored and accumulated. This further increases insulin resistance and leptin resistance.

The result is a vicious circle.


Does A Lack Of Sleep Cause Weight Gain

3. Stress and Cortisol

Sleep affects another hormone, cortisol. Cortisol is generally considered the body’s “stress” hormone.

Mental stress makes your brain unable to relax and calm down. Even if your body is very tired, your brain is still running fast when you are in bed, making it more difficult for you to fall asleep.

The result of this is an increase in cortisol levels. Too much cortisol can mess up your metabolism. At the same time, you may crave sweets or high-fat foods to calm your nerves.

Elevated cortisol levels can also affect glucose metabolism, which can lead to a reduction in fat burning, insulin resistance and inhibit the production of melatonin. 

When you lack sleep, your brain consumes less glucose. This is why you feel fatigued and confused if you don’t sleep well.

4. Melatonin

Melatonin is generally considered the “sleep hormone”. This hormone tells the brain whether it is day or night so that the body adjusts the corresponding metabolic process.

Melatonin also has antioxidant effects, which can help fight disease and inflammation.

However, its most important roles are to increase insulin sensitivity, control the level of energy expenditure and regulate the secretion of leptin and ghrelin.

Indoor light sources, including the blue light emitted by mobile phones and TV, can also affect the production of melatonin. Therefore, if you lie in bed at night and watch your phone in the dark, in addition to being bad for your eyes, it can also reduce the secretion of melatonin.

Maintaining a good sleeping environment contributes to a healthy level of melatonin. It can also help improve insulin sensitivity and help burn body fat.

5. Growth Hormone

This is another hormone affected by lack of sleep. It can help the body produce muscle tissue, increase bone density and help burn fat.

When you are in deep sleep, more growth hormone is released. 

Therefore, even if you sleep for eight hours a night, but your sleep is light, the level of growth hormone may still not be very high.

In other words, in addition to prolonging sleep time, the quality of sleep is also very important.


“There is no doubt that insufficient sleep promotes hunger and appetite, which can cause excessive food intake. All this can result in weight gain,” says Eve Van Cauter, director of the Sleep, Metabolism and Health Center at the University of Chicago. 

Hopefully, this article helps you understand better how a lack of sleep causes weight gain.

If you want to lose weight, be sure to get enough sleep.

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