Extremely overweight teenagers drink and use illegal drugs about as much as their peers, a nationwide survey suggests. But obese teens are more likely to smoke or chew tobacco.

The Los Angeles Times reports that psychologists at the Cincinnati Children’s Hospital Medical Center in Ohio compared 410 teens who were extremely obese—their body-mass index was in the 99th percentile—with 8,669 teens considered to be normal weight. The researchers used the 2007 Youth Risk Behavior Survey, a national survey of high school students conducted by the Centers for Disease Control and Prevention.

In the May issue of Pediatrics, the researchers report that extremely obese boys were more likely to have started smoking before age 13 than their normal-weight male classmates, while obese girls were more likely to have tried smoking, to be a current smoker or to use smokeless tobacco than normal-weight girls.

The study also found that while obese girls were less likely to have had sex than their peers, they were more likely to have used drugs or alcohol before having sex.

The researchers say the findings indicate that health care providers should assess risk-taking behaviors in very overweight teens.