ATLANTA — People who sleep fewer than six hours a night — or more than nine — are more likely to be obese, according to a new government study that is one of the largest to show a link between irregular sleep and big bellies. The study also linked light sleepers to higher smoking rates and alcohol use, and less physical activity.

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, a Colorado physician and a spokesman for the American Academy of Sleep Medicine, Dr. Ron Kramer, said.

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

The study released yesterday is based on door-to-door surveys of 87,000 American adults in 2004- 2006 conducted by the National Center for Health Statistics, part of the Centers for Disease Control and Prevention.

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

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

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

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

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

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.

In another measure, nearly half of those who slept nine hours or more each night were physically inactive in their leisure time, which was worse even than the lightest sleepers and the proper sleepers. Many of those who sleep nine hours or more may have serious health problems that make exercise difficult.

Many elderly people are in the group who get the least sleep, which would help explain why physical activity rates are low. Those skimpy sleepers who are younger may still feel too tired to exercise, experts said.