Contradicting widely held views, a new study has found that consumption of carbonated soft drinks from school vending machines has a negligible impact on adolescent weight problems.

Given that, the data does not support a policy of banning or restricting sales of soft drinks in schools, the authors concluded.

"We don't want this research to be taken to indicate that we think the problem of adolescent overweight is nonexistent or something we shouldn't pay attention to," said study author Richard A. Forshee, deputy director and director of research at the University of Maryland's Center for Food, Nutrition and Agriculture Policy. "We believe adolescent obesity is a very serious problem. We think these kinds of analyses are necessary to help us find most effective interventions so we can have a positive impact on a problem we all care about."

Other nutrition experts argued that the study missed the larger picture.

"You're not going to be able to find one thing that is going to be the be-all and end-all in obesity in kids," said Cathy Nonas, director of the diabetes and obesity programs at North General Hospital in New York City and a spokeswoman for the American Dietetic Association. "I don't think any one thing is going to have a strong effect, but if we don't start to do some of these things now, we don't have a chance in hell of reducing obesity."

The study appeared in the October issue of Risk Analysis, and was funded by the American Beverage Association. Forshee maintained that his group "followed a very rigorous scientific process" and that the association had no input into the analysis, design, interpretation or decision to publish the research. The researchers had initially approached the association for funding.

According to background information in the article, the percentage of adolescents classified as overweight increased from 10.5 percent in the 1988-94 period to 15.5 percent in the 1999-2000 period.

Scientists, policy makers and concerned citizens alike are trying to find effective ways to stem the rising poundage. One strategy under consideration is banning or limiting sales of soft drinks from vending machines in schools.

In January, the American Academy of Pediatrics issued a policy statement recommending that soft drink sales in schools be severely restricted, pointing out that sweetened drinks (including fruit drinks as well as soft drinks) are now the main source of added sugar in the daily diets of children.

The authors of the current study stated there is little scientific evidence to support such a policy, and set out to analyze the existing literature.

To this end, they used the tool of "risk analysis," which, Forshee said, "has not been applied as widely as it should be in nutrition policy."

The idea was to apply the tool to a controversial area in nutrition policy (soft drink sales in schools) as a way to demonstrate that it might have wider utility.

Forshee and his colleagues used two federally funded data sets, including the National Health and Nutrition Examination Survey 1999-2000 (NHANES), and one data set from the National Family Opinion consumer research firm.

The researchers used the largest association between school soft drinks and body mass index (BMI) they could find, which was a .24 unit change in BMI for every one serving change in soft drink consumption.

Even using this upper-end figure, Forshee said, "there was no statistically significant association and, in fact, regular carbonated soft drinks accounted for less than 1 percent of the variance in BMI."

Consumption of soft drinks from school vending machines was also quite low, with estimates ranging from half an ounce to two ounces per day per student. Adolescents drank five times as much at home.

The findings implied that consumption of sugar-sweetened beverages need to be cut by more than four servings a day to reduce BMI by 1 kilogram per meter squared.

With current consumption of such drinks at 2 servings a day for males and 1.2 a day for females, it's unlikely that such a policy in schools will make a "meaningful difference in BMI distribution of the population," the authors wrote.

"We're not saying that there's no kid that has a problem with consumption with sweetened beverages," Forshee said. "We're wondering what kind of public policy interventions are going to be effective at dealing with public health issues."

"Restricting sales of soft drinks in schools does come with some costs," he added. "It restricts choices, and it is a source of revenue for schools."

For Nonas, however, restricting soft drink sales in schools would be part of a larger policy initiative which also would include making parks safer, more gym time in schools, reduced television watching and getting rid of sweetened drinks at home.

"I've always said that vending machines is a start, but nowhere near enough to make a dent," Nonas said. "This, by itself, is not an effective policy. That's different from saying it shouldn't be done."

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