How does sleep affect weight loss?

We take a look at a few studies on the effects of sleep and what we can learn from them.

A lot of studies have been conducted on the effects of sleep or indeed the lack of it over the past few years. 

A lot of conclusions have been drawn but the key takeaways from research suggests the following: sleep recovers your mind and body, deprivation will lead to fat gain and muscle loss, and dieting in tandem with longer sleep aids weight loss whilst preventing muscle loss.

Today, we will be looking at a few studies on the effects of sleep and what we can learn from them.

The different stages of sleep 

Most people are unaware that there are two different types of sleeping. Rapid Eye Movement, also known as REM, is the first type. The second is Non-Rapid Eye Movement, also known as non-REM. Both REM and non-REM are involved in a standard session but in different stages. 

The four stages:

  • STAGE 1: Non-REM: This is the first few minutes of falling asleep. You will feel your heart rate and breathing slow down.
  • STAGE 2: Non-REM: This stage is a period of light sleep before you enter deep sleep. This stage typically lasts for 25 minutes.
  • STAGE 3: Non-REM: This is the longest stage of the cycle. During this stage, the body recovers and regenerates in order to feel refreshed in the morning.
  • STAGE 4: REM: This is the final stage so eye movement and brain activity significantly increases. This is the stage at which most dreams will occur. 

These four stages together make up one sleep cycle. This cycle repeats throughout the night with each cycle taking 90 minutes each time. 

Sleep is Recovery Time

The three fundamentals of healthy living are training, nutrition and recovery. Recovery lets your body build muscle, gain strength and/or lose body fat.

Getting the right amount of sleep every night is essential for recovery in both a performance and health-related perspective.

Emmanuel Mignot published a paper on some key processes that happen overnight to help the body recover. These biological processes include:

  • Cellular and Tissue Restoration: Daily activities stress our body, muscles and tissues. When we rest, these areas are relaxed and repaired, ready for another day of stressors.
  • Improving Brain Function: During sleep, the brain is flushed of waste. Resting helps with learning, memory and improves cognitive function. Deprivation can lead to memory and concentration issues.
  • Energy Conservation: Sleeping reduces energy use during a period when we are not consuming energy. This balances out the body and helps the recovery process, as well as stocking energy for the following day. 

Sleep is crucial for our hormone levels

Rest is also an important time for the release of hormones throughout the body. The hormones released are focused on the following tasks: repairing muscles, regulating appetite, balancing mood and stress levels using neurotransmitters. 

Sleep’s impact on weight

Xuewen Wang conducted a study on the various effects of sleep on the weight of adults. Wang split participants into one group with sufficient rest and one group with deprivation. After the study, Wang found that all participants lost body weight but sleep deprived participants lost the wrong kind of weight: fat-free mass such as muscle and water.

The body produces more cortisol and less testosterone when you are sleep deprived. This means that muscle protein synthesis goes down whilst muscle protein breakdown goes up. This is an unfortunate cocktail for muscle loss and weight gain. 

Sleep must be valued highly if you are looking to gain muscle mass and hit physical goals. Because, depriving yourself of rest will lead to fat build-up and muscle breakdown. 

Other Impacts 

There are of course other studies that delve into more specific sleeping styles. For example, a Brondel study took 12 healthy men and restricted them to 4 or 8 hours in bed. Physical activity was higher for the men with less sleep. 

Another Study found that extending sleep by just one hour can help with weight loss and even has a direct link to decreasing waist circumference. This study also found that extended sleep helped combat inflammation and other metabolic conditions. 


As you can see, it isn’t as simple as saying that deprivation leads to weight gain and energy loss. Sleep is a much more detailed science than many people are aware of. 


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