Girls who aren't concerned about their weight, on the other hand, are much less likely to start puffing, says a study appearing in the September 2003 issue of Tobacco Control.

But the reason, it turns out, is not the obvious one. Girls are not using smoking to control or reduce their weight. Rather, the concern with thinness seems to indicate a poor self-image that predisposes the girls to smoking.

"What's going on is a lot deeper," says the study's senior author, Dr. Michael Siegel, associate professor in the social and behavioral science department at Boston University School of Public Health. "What we're talking about is young girls who are not happy with their body image no matter what it is and are looking for something to improve their identity."

Unfortunately, the tobacco industry is all too eager to provide such an identity, Siegel says. "Tobacco advertises smoking as a way to achieve those things," he says.

This is the first study to look at the importance of being thin as an entry into smoking, the researchers say.

"It's the first to show that overvaluation of thinness is a predictive factor," says Dr. Diane Mickley, co-president of the National Eating Disorders Association (NEDA) Board of Trustees, and founder and director of the Wilkins Center for Easting Disorders in Greenwich, Conn.

Siegel and his colleague, Dr. Kaori Honjo of Okayama University in Japan, based their findings on a 1993 telephone survey of 273 girls aged 12 to 15, all residing in Massachusetts and all selected randomly.

Each girl was asked to rate the value they assigned to being thin, with zero "not at all important" and 10 "extremely important." The same girls were surveyed four years later to see if they had become regular smokers.

In the first survey, only about one in eight girls was overweight, yet 70 percent had tried to diet. The majority (80 percent) said they did not believe smoking was a way to keep weight off.

This finding in itself was striking, say experts. "These were not girls who were actually overweight," Mickley points out. "It's not even real. It's perceptual and it's misguided perception."

The second survey revealed that 23 percent of the girls had become regular smokers (defined as having smoked 100 or more cigarettes total). Those who said being thin was moderately important were more than three times as likely to take up smoking, while those who thought it was very important were more than four times as likely to develop the habit.

Only 7 percent of those who had said thinness was unimportant (scores of zero to four) went on to become smokers. Those girls who said thinness was moderately important (scores of five to seven) represented almost one in four of those who became smokers. Those who rated thinness as extremely important represented almost 30 percent of the smokers.

Unlike many previous studies, there appeared to be no correlation between actual weight or dieting behavior and the likelihood of taking up smoking.

The findings could have implications for smoking-intervention programs, including making girls aware of the marketing techniques employed by tobacco companies, the researchers say.

"I think girls need to be shown in tobacco industry documents that they're purposely trying to recruit young adolescents and that they're trying to go after their psychology," Siegel says. "They are trying to portray smoking as a way for adolescents to achieve an identity. If they (teen girls) are made aware of the techniques used by the tobacco industry in advertising, they will be less likely to choose smoking as a way to achieve identity."

Seeing through the smoke and mirrors could stop kids from lighting up, he adds.

"We need to convince them that smoking is no appropriate way to develop an identity," Siegel says. "In fact, we need to show them the opposite: If you smoke it's not a cool thing to do. It's going to hurt your health. It makes you dependent on this substance, and that's hardly a mature adult thing to do."

"What we're seeing in the study is that overvaluation of thinness is dangerous and leaves vulnerable kids to a variety of self-destructive behaviors," Mickley adds. "You can hurt yourself in a lot of ways if you think anything is worth it to be thin."

NEDA is currently looking at programs that would address both smoking and eating disorders.

Resisting the overtures of big tobacco may ultimately help kids stay away from other unhealthy behaviors as well, the researchers say.

"What this study does is identify a major risk factor for a lot of health issues for girls," Siegel says. "If we can get to the core, we can affect not only smoking risk but a whole host of other issues as well."