Sleep for more (or less) than seven hours a night and you'll put on weight

Seven hours of sleep a night could be the recipe for staying in shape, say researchers.

Too much or too little sleep piles on the pounds, and over the years can end in obesity.

A study has found that those sleeping for less than seven hours a night gained four pounds in six years. Those sleeping for more gained three pounds over the same period.

Healthy: Scientists have revealed that sleeping for seven hours a night could be the secret to maintaining a healthy weight

It is thought that too little or too much sleep causes hormonal changes that may stimulate appetite.

"Both short and long sleeping times predict an increased risk of future body weight and fat gain in adults," said Jean-Philippe Chaput of Laval University in Quebec, where the study was carried out.

"Furthermore, these results emphasise the need to add sleep duration to the list of environmental factors that are prevalent in our society and that contribute to weight gain and obesity."

One third of UK adults regularly sleep five hours or fewer a night, while the average is a healthy seven.

The Canadian study, published today in the medical journal Sleep, looked at 276 adults between 21 and 64 years of age.

Short and long duration sleepers-were 35 per cent and 25 per cent more likely to experience weight gain of 5kg (11lb) compared with average duration sleepers.

Short sleepers gained 1.98kg (4.3lb) on average while long sleepers gained 1.58kg (3.4lb).

The risk of developing obesity was raised for short and longterm sleepers, up by 27 per cent and 21 per cent, compared with those sleeping for an average of seven hours.

The researchers adjusted for age, sex and Body Mass Index - the scale for overweight and obesity which takes several factors into account.

Previous research has suggested that sleep loss could disturb the production of hormones that control the desire for calorierich foods.

The level of ghrelin, a hormone released by the stomach to signal hunger, was found to be 15 per cent higher in people who have only five hours sleep a night compared to those getting eight hours.

Lack of sleep also leads to tiredness during the day, which may mean people do not have enough energy for physical activity.

Those who cut their sleep levels from seven hours to five or fewer face a 70 per cent extra risk of dying from all causes - and twice the risk of death from a cardiovascular problem.

But Professor Jim Horne, director of the Sleep Research Centre at Loughborough University, said those whose sleeping habits exceed seven hours, or who regularly get less, should not despair.

"There is a great deal of evidence now that sleeping less than five hours a night is linked with putting on weight," he said, "but it's a very slow weight gain over a number of years."

Professor Horne's pointers for good sleep hygiene are:

Follow a consistent and relaxing bedtime routine.

Avoid foods and drinks that contain caffeine before going to bed.

Don't take your worries to bed with you.

Don't go to bed hungry, but don't eat a big meal before going to sleep.

Make your bedroom quiet, dark and a little cool.

Get up at the same time every morning.

If you can't sleep, leave the bedroom, do a jigsaw in dim light and wait for the eyelids to close.

By JENNY HOPE - at 23:31pm on 1st April 2008
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