People who sleep fewer than six hours a night, or more than nine, are more likely to be obese, a new government study says.

According to the Associated Press, the study is one of the largest to show a link between irregular sleep and big bellies.  The new research also linked light sleepers to higher smoking rates, less physical activity and more alcohol use.

Dr. Ron Kramer, a Colorado physician and a spokesman for the American Academy of Sleep Medicine, says the study adds weight to a stream of studies that have found obesity and other health problems in those who don’t get proper shuteye.

“The data is all coming together that short sleepers and long sleepers don’t do so well,” Kramer said.

The study is based on door-to-door surveys of 87,000 U.S. adults from 2004 through 2006 conducted by the National Center for Health Statistics, part of the Centers for Disease Control and Prevention, AP said.

Charlotte Schoenborn, the study’s lead author, says such surveys can’t prove cause-effect relationships, so—for example—it’s not clear if smoking causes sleeplessness or if sleeplessness prompts smoking.

It also did not account for the influence of other factors, such as depression, which can contribute to heavy eating, smoking, sleeplessness and other problems, she said.

Smoking was highest for people who got under six hours of sleep, with 31 percent saying they were current smokers. Those who got nine or more hours also were big puffers, with 26 percent smoking, AP said.

The overall U.S. smoking rate is about 21 percent. For those in the study who sleep seven to eight hours, the rate was lower, at 18 percent.

Results were similar, though a bit less dramatic, for obesity: About 33 percent of those who slept less than six hours were obese, and 26 percent for those who got nine or more. Normal sleepers were the thinnest group, with obesity at 22 percent.

For alcohol use, those who slept the least were the biggest drinkers. However, alcohol use for those who slept seven to eight hours and those who slept nine hours or more was similar, AP said.