XXL from too few Zs? Skimping on sleep might cause obesity, diabetes.

Widespread sleep deprivation could partly explain the current epidemics of both obesity and diabetes, emerging data suggest.

Too little sleep may contribute to long-term health problems by changing the concentrations of hormones that control appetite, increasing food intake, and disrupting the biological clock, according to Eve Van Cauter of the University of Chicago.

Van Cauter and other researchers discussed possible links between sleep deprivation, expanding waistlines, and obesity-related problems this week in Washington, D.C., at a meeting titled A Scientific Workshop on Sleep Loss and Obesity: Interacting Epidemics.

Researchers have observed that people who sleep less than 7 to 8 hours a night have elevated rates of obesity and diabetes. In late 2004, Karine Spiegel of the Free University of Brussels in Belgium and Van Cauter conducted experiments in healthy men showing that forced sleep restriction for 2 days increased appetite and triggered changes in the appetite-related hormones ghrelin and leptin (SN: 4/2/05,p. 216). The observed ghrelin elevation and leptin suppression may have encouraged food intake, Spiegel says.

Before that pivotal study, tests had demonstrated that obesity could disrupt sleep, but few experiments had investigated whether lack of sleep could contribute to obesity.

Preliminary results close in on an independent relationship between sleep loss and diabetes. Spiegel, Van Cauter, and their colleagues collected data from 13 volunteers who habitually sleep about 5 hours per night and from 14 others who sleep about 8 hours per night. The groups had similar body weights and ages.

Spiegel reported at the conference that the people who sleep less produce markedly elevated quantities of the hormone insulin. Their high insulin production reflects a state, called insulin resistance, that can be a harbinger of diabetes, Spiegel says.

In another new study reported at the conference, Emmanuel Mignot of Stanford University Medical School and his colleagues tested about 2,000 employees of Wisconsin government agencies. Obesity was common in that population, and volunteers who slept either significantly less or more than the overall average tended to be heavier than people getting a moderate amount of sleep, Mignot reports. Compared with people who slept 8 hours a night, those who slept 5 hours had 16 percent lower leptin concentrations and 15 percent higher ghrelin concentrations in their blood.

Mignot and his colleagues have launched a yearlong trial that will test whether prescribing extra sleep can make some obese people lose weight. He hypothesizes that an extra 1.5 hours of sleep per night might produce weight losses of 3 to 4 percent.

But Van Canter says that when her team previously asked patients to increase nightly sleep for extended periods of time, the changes in behavior lasted only a few days.

Short sleep might encourage overeating independent of its hormonal effects, says Mignot. "When people sleep less, they have more time for eating," he notes.--B. HARDER