ATLANTA -- A new government study found that people who sleep fewer than six hours a night -- or more than nine -- are more likely to be obese.

The research is one of the largest studies to show a link between irregular sleep and big bellies.

The study 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, said the research adds weight to a stream of studies that have found obesity and other health problems in those who don't get proper shuteye.

The study was conducted by the National Center for Health Statistics and is based on door-to-door surveys of 87,000 U.S. adults from 2004 through 2006.