How sleep affects your weight

Nutrition Action Healthletter, July-August, 2005 by David Schardt

When the University of Chicago's Eve Van Cauter and her colleagues limited 11 healthy men in their 20s to four hours of sleep for six straight nights, "it brought them to a nearly prediabetic state."

Their bodies were 40 percent less able to clear glucose from their blood and 30 percent slower in releasing insulin than when they were allowed to sleep for twelve hours. (3) In fact, four hours of sleep for six consecutive nights gave the young men the insulin sensitivity of 70- or 80-year-olds.

"We didn't expect to see a change of that magnitude," says Van Cauter.

(Insulin is a hormone that lets glucose, or blood sugar, enter the body's cells, where the sugar is burned for energy. When people are insulin insensitive, or insulin resistant, their insulin doesn't work efficiently.)

"The consensus that prevailed until recently was that sleep is for the brain, not for the rest of the body," says Van Cauter. "But sleep really affects everything. We are not wired biologically for sleep deprivation. We're the only animal that intentionally sleeps less than we need to."

(1) PLoS Med. 1:e62 2004 (Epub.).

(2) Ann. Intern. Med. 141: 846, 2004

(3) Lancet 354: 1435, 1999

RELATED ARTICLE: Sleepus interruptus.

Sleep less, weigh more. If true, that's not good news for the estimated 15 million Americans with sleep apnea

Sleep apnea (pronounced APP-knee-uh) typically occurs when the soft tissue in the rear of the throat relaxes too much during sleep, partially blocking the passage and cutting off the flow of air. The result: loud snoring and labored breathing. If the passage closes entirely, no air can get through and breathing stops until the brain rouses the person enough to gasp for air.

According to the American Sleep Apnea Association in Washington, D.C., some people with untreated apnea stop breathing hundreds of times during the night, often for a minute or longer. When they do fall back to sleep, it's generally to a lighter, fragmented, less-restful stage that leaves them drowsy the next day.

It's not a minor problem: the number of Americans who have sleep apnea equals the number who have diabetes. And, like those with diabetes, "the majority don't know it or aren't being properly treated," says Sleep Apnea Association president Rochelle Goldberg.

What's more, apnea "increases your risk for developing high blood pressure, coronary heart disease, and diabetes, for suffering strokes, and for having accidents during the day."

How? "Obstructed breathing produces an arousal response that revs up the body into a 'fight-or-flight' stance," she explains. To divert blood to high-priority sites, the blood vessels constrict and the heart rate increases. "Since the oxygen supply is cut off at the same time, the circulatory system can be damaged, especially if it happens again and again every night."

And it's not just the blood vessels that pay. People with severe sleep apnea--that means at least 15 breathing disruptions an hour--suffer a loss of motor skills, attention, and concentration that's equal to an additional five years of aging/