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Why Sleep Is So Important for Losing Weight

Hayley Dawes
22 January 2023

When it comes to weight loss, diet and exercise are usually thought of as the two key factors that will achieve results. However, sleep if an often-neglected lifestyle factor that also plays an important role. People and weight loss programs often over-look sleep and it might just be the reason why you aren’t losing any weight even with slashing calories and exercising every single day of the week. So, are you getting enough sleep? The recommended sleep duration for adults is seven to nine hours a night, but many people often sleep for less than this. 

Research has shown that sleeping less than the recommended amount is linked to having greater body fat, increased risk of obesity, and can also influence how easily you lost weight on a calorie-controlled diet. Sleeping for less than five hours even for a single night considerably increases your chances of gaining weight, particularly belly fat. Even though calorie-deficit diet and exercise are important factors that lead up to weight loss – sleep deprivation can do the exact opposite. 

Typically, the goal for weight loss is usually to decrease body fat while retaining as much muscle mass as possible. Not obtaining the correct amount of sleep can determine how much fat is lost as well as how much muscle mass you retain while on a calorie restricted diet.

Metabolism & Appetite 

There are several reasons why shorter sleep may be associated with higher body weight and affect weight loss. These include changes in metabolism, appetite, and food selection.

Even the best diet and hours of exercise will not help you with losing weight if you don’t get 7 to 8 hours of uninterrupted sleep. Sleep deprivation affects important hormones that are essential to lose weight. Low number of sleeping hours decreases leptin (satiety hormone), increases ghrelin (hunger hormone), and also shoots up cortisol (the stress hormone). Without enough sleep, these hormones will go out of sync, you would wake up with a slow metabolism and a ravenous appetite, making you crave for sugary and high-calorie foods because your brain is looking for instant energy to make up for the lack of sleep. Also, lack of

Sleep influences two important appetite hormones in our body:


This is a hormone that decreases appetite, so when leptin levels are high, we usually feel fuller.


On the other hand, ghrelin is a hormone that can stimulate appetite, and is often referred to as the “hunger hormone” because it’s thought to be responsible for the feeling of hunger. 

Consequently, increased food intake due to changes in appetite hormones may result in weight gain. This means that, in the long term, sleep deprivation may lead to weight gain due to these changes in appetite. So, getting a good night’s sleep should be prioritised.

Along with changes in appetite hormones, reduced sleep has also been shown to impact on food selection and the way the brain perceives food.

Researchers have found that the areas of the brain responsible for reward are more active in response to food after sleep loss when compared to people who had good sleep. This could possibly explain why sleep-deprived people snack more often and tend to choose carbohydrate-rich foods and sweet-tasting snacks, compared to those who get enough sleep.



The sleep hormone melatonin enables one to have a good night’s sleep. Optimum levels of melatonin boosts metabolism, accelerates fat burning, and prevents insulin resistance. Our brain starts pumping out melatonin after sundown when the body is ready to go into the rest mode. However, exposure to blue light through gadget (phone, tv, etc.) can disrupt the sleep-wake cycle, also called the circadian rhythm of the body, and cause disruption in melatonin release, severely affecting the quality of sleep. A disruption in circadian rhythm can trigger a lot of health problems – from insulin resistance to depression, and that’s why sleeping for at least 7 hours every night matter, from lowering stress to losing weight. 

Sleep duration also influences metabolism, particularly glucose (sugar) metabolism.

When food is eaten, our bodies release insulin, a hormone that helps to process the glucose in our blood. However, sleep loss can impair our bodies’ response to insulin, reducing its ability to uptake glucose.

We may be able to recover from the occasional night of sleep loss, but in the long term this could lead to health conditions such as obesity and type 2 diabetes.

Given that sleep-deprived people already tend to choose foods high in glucose due to increased appetite and reward-seeking behaviour, the impaired ability to process glucose can make things worse. An excess of glucose (both from increased intake and a reduced ability to uptake into the tissues) could be converted to fatty acids and stored as fat. Collectively, this can accumulate over the long term, leading to weight gain.

However, physical activity may show promise as a countermeasure against the detrimental impact of poor sleep. Exercise has a positive impact on appetite, by reducing ghrelin levels and increasing levels of peptide YY, a hormone that is released from the gut, and is associated with the feeling of being satisfied and full.

Research has also shown that exercise training may protect against the metabolic impairments that result from a lack of sleep, by improving the body’s response to insulin, leading to improved glucose control. 

It’s clear that sleep is important for losing weight. A lack of sleep can increase appetite by changing hormones, makes us more likely to eat unhealthy foods, and influences how body fat is lost while counting our calories. 

To get a good night’s sleep – stay away from blue light one hour before sleep because exposure to light and blue light from gadgets can disturb the circadian rhythm of the body. Make it a point to eat at least two to three hours before sleep because having dinnertime and bedtime too close to each other keeps the digestive system active and prevents you from having a good night’s sleep.

Sleep should therefore be considered as an essential alongside diet and physical activity as part of a healthy lifestyle.