When it comes to losing weight, diet and exercise are usually considered the two key factors that will achieve results. However, sleep is a lifestyle factor that is often overlooked and also plays a significant role. The recommended sleep duration for adults is seven to nine hours per night, but many people tend to sleep less. Research has shown that sleeping less than the recommended amount is linked to having a higher amount of body fat, a higher risk of obesity, and it can also influence how easily you lose weight on a calorie-controlled diet.
Usually, the goal of weight loss is to decrease body fat while preserving as much muscle mass as possible. Not getting the right amount of sleep can determine the amount of fat you lose and the amount of muscle mass you retain while following a calorie-restricted diet. One study found that sleeping 5.5 hours each night over a two-week period on a calorie-restricted diet resulted in less fat loss compared to sleeping 8.5 hours each night. But it also resulted in a greater loss of fat-free mass (including muscle).
Another study showed similar results over an eight-week period when sleep was reduced by just one hour each night for five nights of the week. These results showed that even catching up on sleep over the weekend may not be enough to reverse the negative effects of sleep deprivation while following a calorie-controlled diet.
Metabolism, appetite and sleep.
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.
Our own research has shown that a single night of sleep restriction (only four hours of sleep) is enough to affect the insulin response to glucose intake in healthy young men. Since sleep-deprived people already tend to choosehigh-glucose foods due to increased appetite and reward-seeking behavior, the impairment in the ability to process glucose may make things worse.
Sleep influences two important appetite hormones in our body: leptin and ghrelin. Leptin is a hormone that decreases appetite, so when leptin levels are high, we tend to 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 is thought to be responsible for the feeling of hunger.
One study found that sleep restriction increases ghrelin levels and decreases leptin levels. Another study, which included a sample of 1024 adults, also found that short sleep was associated with higher levels of ghrelin and lower levels of leptin. This combination could increase a person’s appetite, making calorie restriction more difficult to adhere to and may make a person more prone to overeating.
Consequently, increased food intake due to changes in appetite hormones can lead to weight gain. This means that, in the long term, lack of sleep can lead to weight gain due to these changes in appetite. Therefore, a good night’s sleep should be prioritized.
We have also shown the potential benefits of a single session of exercise on glucose metabolism after sleep restriction. While this seems promising, studies still need to determine the role of long-term physical activity in people with sleep problems.
Along with changes in appetite hormones, sleep reduction has also been shown to affect 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 (six nights of only four hours of sleep) compared to people who slept well (six nights of nine hours of sleep).
This could possibly explain why sleep-deprived people snack more frequently and tend to choose high-carbohydrate and sweet snacks, compared to those who get enough sleep.
Sleep duration also influences metabolism, particularly glucose (sugar) metabolism. When we eat food, our body releases insulin, a hormone that helps process the glucose in our blood. However, lack of sleep can affect our body’s response to insulin, reducing its ability to absorb glucose. We may be able to recover from an occasional night of sleep loss, but in the long term, this could lead to health problems such as obesity and type 2 diabetes.
An excess of glucose (both from increased intake and reduced ability to absorb into tissues) could be converted into fatty acids and stored as fat. Collectively, this can accumulate over the long term, leading to weight gain.
However, physical activity may prove promising as a countermeasure against the detrimental impact of lack of sleep. Exercise has a positive impact on appetite, reducing ghrelin levels and increasing levels of peptide YY, a hormone that is released in the gut and is associated with feeling satisfied and full.
After exercise, people tend to eat less, especially when considering the energy expended by exercise. However, it is unknown whether this still remains in the context of sleep restriction.
Research has also shown that physical training can protect against metabolic deficiencies resulting from lack of sleep, by improving the body’s response to insulin, leading to better glucose control.
It is clear that sleep is important for weight loss. Lack of sleep can increase appetite by changing hormones, makes us more prone to eat unhealthy foods, and influences how body fat is lost when counting our calories. Therefore, sleep should be considered essential along with diet and physical activity as part of a healthy lifestyle.
Authors: Emma sweney Professor of Exercise and Health, Nottingham Trent University Ian Walshe Professor of Health and Exercise Sciences, University of Northumbria, Newcastle Originally published in: https://theconversation.com/why-sleep-is-so-important-for-losing-weight-145058