November 27, 2004
TOO fat for your own good? Few will be convinced that it's really your big bones, glands or genes that are to blame. For most people, it is a case of giving up junk food, sticking to a balanced diet and taking more exercise in order to lose excess weight.

The message is clear, but perhaps we should add "Are we getting enough sleep?", because the most unconvincing excuse for excessive weight has just been backed up by respectable scientific evidence.

At a meeting of the North American Association for the Study of Obesity last week, scientists reported finding a strong link between the amount of sleep you have and your chances of being obese.

"People who were getting an average of less than four hours sleep a night were 73per cent more likely to be obese than those getting the recommended seven to nine hours," said lead researcher James Gangwisch, an epidemiologist at the Mailman School of Public Health and the Obesity Research Centre of Columbia University in New York.

He and his team had analysed data from 18,000 adults taking part in a survey started in the 1980s. They found having five hours sleep led to a 50per cent risk of obesity. This fell to 23per cent with six hours.

You might think that tossing and turning would burn off calories rather than pile on the pounds. But because of the way our bodies are wired, sleep and weight are closely connected. A recent study at Chicago University, for instance, found that allowing normal subjects only four hours sleep for just two nights directly affected key chemicals that control weight. Levels of leptin, a protein that sends "I'm full" messages, dropped by 20per cent, and the amount of a peptide called ghrelin, which makes you feel hungry, rose by 20per cent.

One expert suggested this mechanism evolved to allow us to store fat in periods of less sleep, such as the summer, to keep us going through the winter.

So could lack of sleep - only about 30per cent of us regularly get the recommended amount - rather than Big Macs and a couch-potato lifestyle explain what has been called "the obesity epidemic"?

And could getting enough sleep help you lose weight?

Two other recent pieces of research have confirmed that our night habits do play a role in the battle of the bulge. Another team at last week's conference highlighted the damage that can be done by midnight raids on the fridge. University of Pennsylvania researchers have identified what they call "night-eating syndrome" - sufferers consume up to 30per cent of their calories through the night, usually cakes, biscuits, ice cream and other high-fat sugary foods.

One theory is that far from being just greedy they are engaging in self-medication: all those carbohydrates increase levels of the feel-good brain chemical serotonin. Another small study found that the serotonin-boosting antidepressant Zoloft (sertraline) reduced the number of fridge visits.

But extra serotonin can also interfere with sleep because normally serotonin levels drop effectively to zero when people are dreaming in rapid-eye-movement sleep.

Personally, i am one that needs convincing about this. Last year, i was at my peak fitness wise, excersing 2 hrs a day 5 days a week. I did whilst working and studying, therefore sleep was little, around 5 hrs a night. I had never felt so good in my life, there would have been no way i'd have been able to sustain that lifestyle ( little sleep) without the exercise. These days i feel like a blimp, get about 7 hrs and am wrecked during the day. I am going back to my exercising life.