Research found obesity doubled in the population while the average number of hours slept per night was reduced

New evidence links obesity with sleep deprivation

According to new research, there might be an easy way to keep trim…

stay in bed. Roger Highfield reports on evidence linking obesity with sleep deprivation

The discovery is enough to make you lose sleep: evidence is emerging of a link between a drop in the time society spends slumbering and the dramatic rise in obesity and associated diseases, such as diabetes and high blood pressure

A flurry of worldwide research has established an intriguing connection between poor sleep and fat stomachs. This has a range of fascinating implications. Levels of obesity could be significantly cut by having a lie-in. Earlier bedtimes and later waking times could be an important, low-cost way to shrink waistlines. And children, in particular, could benefit.

One study featuring 18,000 adults participating in the US Government’s National Health and Nutrition Examination Survey throughout the Eighties revealed a surprisingly strong link between waistlines and snoozing. Those who got fewer than four hours of sleep a night were 73 per cent more likely to be obese than those who got the recommended seven to nine hours. Those who averaged five hours had a 50 per cent greater risk, while those who got six hours had a 23 per cent greater risk.

“Maybe, there’s a window of opportunity for helping people sleep more, and maybe that would help their weight,” said Steven Heymsfield of Columbia University and St Luke’s-Roosevelt Hospital in New York, who did the work with James Gangwisch at Columbia. A subsequent study by the same team also linked lack of sleep with high blood pressure.

The sleep-weight link initially perplexed researchers. More time awake should mean more calories burnt. But people also eat when they’re awake, and the effect of chronic sleep deprivation on the brain’s food-seeking circuitry is what seems to be influencing obesity as well as raising the risk of insulin resistance, diabetes and heart disease.

One clue may lie in a type of brain cell found while studying narcolepsy, a condition marked by sudden bouts of deep sleep. These cells control our feeding and sleep circuits with the aid of chemicals called orexins. A lack of orexins makes people fall asleep, the right amount ensures both normal sleep and appetite.

Researchers have also found that not enough sleep causes changes in hormones that regulate appetite. Dr Shahrad Taheri from Bristol University, and colleagues in the University of Wisconsin and Stanford in America, examined the role of two hormones, leptin and ghrelin, in more than 1,000 volunteers under “real-life” conditions. Low levels of leptin and high levels of ghrelin will make you feel hungry.

Dr Taheri said: “We found that people who slept for shorter durations have reduced leptin and elevated ghrelin. Individuals who spent fewer than eight hours sleeping were shown to have a greater likelihood of being heavier.” People who habitually slept for five hours were found to have 15 per cent more ghrelin than those who slept for eight hours. Complementing this was a 15 per cent fall in leptin. The bleary-eyed also seem to crave carbohydrate-rich foods.

The research to date chimes with the warning of many chronobiologists that our Stone Age bodies are not suited to today’s 24/7 lifestyle. There is evidence that we have reduced the amount of time we spend asleep by up to two hours a night because of increasing pressures on our time, whether from work, school, family, television, computer games or the internet, said Dr Taheri.

He added that it is telling that between 1960 and 2000, the prevalence of obesity doubled in the population while the average number of hours slept per night was reduced. During the same period, the percentage of young adults who slept fewer than seven hours rose from 16 per cent to 37 per cent. Meanwhile, strenuous outdoors activity that helps us get a good night’s sleep has declined.

Even if the effects of shut-eye are not yet fully understood, and even if they only have a relatively small influence on body weight, they merit more study. Such is the scale of the obesity epidemic that if a simple measure such as encouraging children to sleep for a little longer has a measurable effect, this may be a potent new weapon in the fight against flab