How does sleep affect weight loss?

Does sleep affect weight loss? It's an important question, especially If you are dieting and exercising in a bid to shed some pounds. Good sleep is just as vital as moving and fueling our bodies, as it gives us time to rest and reset. 

Professionals say that we should be getting on average 6-8 hours of sleep a night, but for many of us, stressful jobs, families or even technology means we’re not getting anything like that amount of sleep each night. When we don’t get enough sleep it affects how we function and ultimately our eating habits. But can we lose calories as we sleep and how does lack of snoozing ultimately affect our appetite? 

• Related: How sleep affects the brain

Does sleep affect weight loss?

Believe it, or not, we actually burn calories as we sleep - but of course, we all burn a different amount of calories, just like we do when we’re awake. Most people burn an average of 50 calories an hour when asleep, but the exact amount is based on our personal basal metabolic rate (BMR) - and of course the more sleep we get the more calories we burn. So someone who only sleeps an average of 5 hours a night is more likely to burn less calories than someone who regularly gets 8 hours a night. This is why it can be important to learn how to sleep for longer if you generally don't get much sleep. 

And it’s a lack of sleep that could affect our attempts to lose weight, as Flo Seabright - Nutritionist and founder of FBF Collective told Live Science: "Lack of sleep can impact food choices, whether that’s because adhering to a 'normal' healthy, balanced diet just feels more difficult when you’re sleep deprived or because we opt for foods that we feel will give us more energy, such as sugary or sweet foods."

Seabright also said that, when it comes to sleep, it really is quality over quantity: "Quality sleep is key in order to allow your body to function optimally and is an important way in which your body can recover and perform key biological processes, such as hormone regulation - including those hormones related to hunger, appetite and satiety."

Does sleep affect weight loss: lack of sleep and appetite

Hormones play a big part in regulating or increasing our appetites - for instance most of us feel hungrier than normal when we've drunk alcohol the night before, normally because we’ve had less quality sleep and our hormones have been disrupted.

PLos Med research shows that when ghrelin and leptin, the two hunger hormones, are impacted, with disruption to sleep, it can change our diets or how much we crave food. Ghrelin, a hormone which helps to tell you you're hungry, is released when you have an empty stomach, while Leptin helps to suppress hunger and informs the brain when we’re hungry.

However, Seabright said: "Sleep is key for our body to regulate these hormones. When the body is not able to regulate these properly, the result can be increased hunger levels and reduced satiety, which make it more difficult to  adhere to a nutritionally optimal diet."

In fact the research around these two hormones, with over 1000 people, found that participants who slept for shorter periods, than those who had a good night's sleep, had higher (14.9%) ghrelin levels and lower (15.5%) leptin levels. While BMI levels were also higher in the participants who slept for less hours each night.

"When we don’t get enough sleep, ghrelin, the 'hunger hormone’, and leptin, the 'satiety hormone’, can become imbalanced leading to increased feelings of hunger and reduced satiety throughout the day," Seabright explained, "Not only do you feel hungrier, but you are less able to recognise when you are full!"

Does sleep affect weight loss: does sleeping naked help you lose weight?

Whether you love to slip into your favourite PJs or something a little less restrictive, research has shown that sleeping naked does have many benefits, when it comes to weight loss. You may want to snuggle up in different layers, especially in the winter, but studies have shown that the lower your body temperature is, while you sleep, the better it is for losing those pounds.

Studies have shown that our body temperature impacts not just our quality of sleep, but also how our metabolism reacts. Research by the US National Institutes of Health studied a group of men, in a cooler environment for over a month and found that it sped up their metabolism, and burnt brown fat, in a bid to make them warmer while they slept. 

The job of the brown fat, which is also known as adipose tissue, is to help you stay warm when you get cold -  it becomes activated when your body temperature is at a certain temperature and therefore is burnt more easily when you’re cold.