A good night's sleep helps cut appetite by up to 500 calories a day, according to a new study.

Getting enough sleep could save millions of people from putting on unwanted weight, say scientists.

It is estimated that two out of every three men and six out of 10 women in England are either obese or overweight.

Obesity increases a person's chances of suffering from mental health problems and has been linked with heart conditions, diabetes, and cancer, all leading causes of death.

Now scientists at the University of Chicago Medicine have come up with a simple solution which many people are likely to welcome; that's getting more snoozing in.

Author Dr Esra Tasali said, "Over the years, we and others have shown that sleep restriction has an effect on appetite regulation that leads to increased food intake, and thus puts you at risk for weight gain over time.

"More recently, the question that everyone was asking was, ‘Well, if this is what happens with sleep loss, can we extend sleep and reverse some of these adverse outcomes?'"

The researchers recruited 80 young, overweight adults, who would usually only sleep for six and half hours a night.

They were asked to wear a sleep monitor and given counseling sessions to bring their shut eye up to eight and half hours per night.

This way, participants were able to continue sleeping in their own beds and did not have to change their diets.

Dr Tasali said, "Most other studies on this topic in labs are short-lived, for a couple of days, and food intake is measured by how much participants consume from an offered diet.

"In our study, we only manipulated sleep, and had the participants eat whatever they wanted, with no food logging or anything else to track their nutrition by themselves."

Participants increased their average sleep duration by over an hour a night after just one counseling session.

To track their calorie intake, the researchers used a special urine test called the "doubly labelled water method."

It involves giving participants water where the hydrogen and oxygen atoms have been replaced with less common harmless substances.

Senior author Professor Dale Schoeller said, "This is considered the gold standard for objectively measuring daily energy expenditure in a non-laboratory, real-world setting and it has changed the way human obesity is studied."

People who get more sleep reduce their calorie intake by an average of 270 kcal per day, with some even cutting out 500, the researchers found.

This translates to roughly 12 kg [26 lbs] of weight loss over three years, provided the effects were maintained over a long term.

Dr Tasali said, "We saw that after just a single sleep counselling session, participants could change their bedtime habits enough to lead to an increase in sleep duration.

"We simply coached each individual on good sleep hygiene, and discussed their own personal sleep environments, providing tailored advice on changes they could make to improve their sleep duration.

"Importantly, to blind participants to sleep intervention, recruitment materials did not mention sleep intervention, allowing us to capture true habitual sleep patterns at baseline."

The study lasted four weeks, with the first two being dedicated to finding out how many hours participants enjoyed.

Dr Tasali said, "This was not a weight-loss study.

"But even within just two weeks, we have quantified evidence showing a decrease in caloric intake and a negative energy balance—caloric intake is less than calories burned."

A healthy sleep pattern could therefore be used to combat obesity, which affects around 13 percent of the world's population.

Dr Tasali said, "If healthy sleep habits are maintained over longer duration, this would lead to clinically important weight loss over time.

"Many people are working hard to find ways to decrease their caloric intake to lose weight —well, just by sleeping more, you may be able to reduce it substantially."

The findings were published in the journal JAMA Internal Medicine.

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