Why is sleep important to weight loss?

Why is sleep important to weight loss?

All the talk is about dieting and exercise when you’re losing weight. “Move more and eat less” is good advice, but it neglects a critical factor in weight loss – sleep.

In hundreds of scientific papers, short sleep —fewer than 6–7 hours — is linked to a higher body mass index (BMI) and weight gain.

This randomised study of adults found that sleep curtailment (5.5 hours versus 8.5 hours) decreased weight loss as fat by 55% and increased the loss of fat-free body mass by 60% (in other words, it increased muscle loss by 60%).

Ultimately, sleep impacts weight loss, and there are several reasons why. This article runs through everything you need to know.

How sleep impacts weight loss

Why is sleep important to weight loss? PIctured: Overweight man asleep doing exercise routine.
PIctured: Overweight man asleep doing exercise routine.

Inadequate sleep has the following effects on weight loss:

  • Increases insulin resistance, which can lead to diabetes and weight gain.
  • Interferes with the body’s production of metabolic hormones.
  • Reduces the production of HGH (Human Growth Hormone), which plays a role in muscle growth and fat storage.
  • Interferes with the body’s ability to metabolise carbohydrates, increasing body-fat storage and hindering weight loss.

The scientific consensus on sleep and weight loss

This analysis of 20 studies into sleep duration and obesity concludes that short sleep duration increases the risk of obesity. This analysis of 17 studies into sleep deprivation and energy balance concludes that sleep deprivation increases energy intake from high-fat, low-protein foods, contributing to weight gain.

Lack of sleep boosts body-fat storage. 

Your body creates glucose by breaking down carbohydrates from the foods you eat. A lack of sleep interrupts this process, boosting body-fat storage by reducing your body’s ability to metabolise glucose into energy.

When this happens, your body preserves glucose and stores it as fat, contributing to weight gain and hindering weight loss efforts.

Lack of sleep hinders HGH release.

The release of Human Growth Hormone is dependent on sleep, and low HGH is linked to weight gain and central obesity.

Adequate sleep boosts the amount of Human Growth Hormone released in the body, contributing to weight loss and maintenance. HGH deficiency is found in people with a high BMI, which suggests higher levels of sleep disruption from obesity.

Lack of sleep makes you sniff out calorie-dense foods  

High Calories Foods.Why is sleep important to weight loss?
Pictured: High Calories Foods.

Researchers have found that a lack of sleep changes how the olfactory system (sense of smell) responds to food odours and how those signals are communicated with the brain.

When sleep-deprived, your olfactory system is in overdrive to sniff out calorie-dense and high-fat foods. There is also a communication breakdown with other brain areas, intensifying the appetite for energy-rich foods.

Without exercising self-control, this inevitably leads to choosing foods with a richer energy signal, increasing your consumption of junk foods.

Lack of sleep disrupts your metabolic hormone function 

Another reason a lack of sleep increases appetite is it affects the production of metabolic hormones Leptin and Ghrelin, which regulate appetite.

Why is sleep important to weight loss? Food intake Illustration.
Pictured: Food intake Illustration.

A study in 2004 found that sleep plays a critical role in circulating levels of Leptin. Leptin signals energy balance to the brain, and a lack of sleep reduces Leptin levels, impacting how the brain perceives energy requirements.

Short sleep duration and high body mass index (BMI) is linked across all ages. This 2021 study found a direct link between obesity and diabetes with Leptin and Ghrelin. In conclusion: sleep is the key to healthy metabolic hormone function.


Sleeping more will help you lose weight faster, providing you continue to control your calorie intake and lead an active lifestyle.

Adequate sleep is essential for metabolic hormone regulation and breaking down glucose into energy. Low sleep duration increases appetite and insulin resistance and affects HGH levels, contributing to weight gain.

Sleep is as essential as diet and exercise if you want to lose weight. Please read our article 10 Tips For Better Sleep at Night in 2022 to learn how to sleep better.

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