Science News

Eat, sleep and be skinny

Researchers have shown that, somewhat surprisingly, the key to preventing children from becoming overweight is a good nights sleep.

A growing body of evidence now links lack of sleep, increased appetite and weight gain amongst adults, but it wasn't clear whether the same applies to children as they grow up.  A few studies have hinted at higher obesity rates amongst youngsters who take the least sleep, but it wasn't clear which effect came first, and whether being overweight just leads to poorer quality sleep.

To find out Julie Lumeng and her colleagues at the University of Michigan enrolled nearly 800 nine year olds and followed them up for three years, to see whether their sleep patterns (reported by their mothers) were related to changes in weight as they grew up.  The results were astonishing.  The children getting less than nine hours shut-eye per night were much more likely to pile on the pounds over the next three years than their superiorly-slumbering counterparts.  Even more striking was the finding that every extra hour of sleep the children took at the age of nine resulted in a 40% decrease in obesity risk by the age of twelve.  And at age twelve each extra hour reduced the risk by 20%.  The researchers cannot say for certain why extra sleep should keep kids in trim, but there are several explanations.

"Children who are better rested may have more energy to get more exercise," explains Lumeng. "It's also possible that when children are tired they may be more irritable or moody and use food to regulate their mood." It's likely that hormones also play a role.

Amongst adults, sleep deprivation has been linked to a reduction in levels of the appetite-suppressing hormone leptin, and increased production of the appetite-boosting hormone ghrelin.  These changes translate into a stronger urge to eat, increased calorie intake and weight gain.  So, paradoxically, kids might be able to justify missing the school bus in future on the grounds that they're battling the bulge...with a lie-in!

11th Nov 2007