"These are the kids you expect least to change," said Gary D. Foster, director of Temple University's Center for Obesity Research and Education, who chaired the study of 4,603 students in 42 middle schools around the country, including six in Philadelphia. He and others speculated that the decline might be greater in the general population.
Though good news, the finding was not what the researchers were looking for. Their primary goal was to determine whether an intensive, school-based effort to decrease calories and increase physical activity could make a dent in the combined prevalence of children who are overweight and obese, key risk factors for Type 2 diabetes.
In fall 2006, they divided the schools into two groups. The sixth graders in half the schools participated in the program; the other half were controls. When they were reassessed as eighth graders in spring 2009, the rate of overweight and obese students had dropped by nearly the same 4 percent in the schools that got the intervention as in those that did not.
However, the researchers did find notable differences among subgroups and in specific measures. For example, body-mass index scores, average insulin levels and the percentage of students with the largest waists - all risk factors for Type 2 diabetes - were significantly better in the intervention schools. All the effects were even stronger among students who were overweight or obese when they began the program in sixth grade. That group, in fact, had 21 percent lower odds of being obese at the end of eighth grade compared with the controls.
Foster and colleagues presented the findings Sunday at the association's annual scientific meeting in Orlando. Underscoring their significance, the results were simultaneously published online in the New England Journal of Medicine.
Type 2 diabetes, until recently seen only in adults, has been increasing steadily in children and teenagers. The Centers for Disease Control and Prevention projects that one of every three children born in 2000, and one of every two children in high-risk minority groups, will develop diabetes in their lifetimes. People with Type 2 diabetes gradually lose the ability to produce insulin and are at risk of kidney failure, amputations, blindness, heart disease, and stroke.
For the new study, teams of researchers developed a program to change nutrition and physical activity in the schools, bolstered by classroom curricula and communication strategies to explain and support the changes. To control nutrition, for instance, all vending machines were limited to items with 200 or fewer calories, all sugar-sweetened beverages and milk with more than 1 percent fat were removed from the schools, and offerings were changed not just in the cafeteria but at fund-raisers and school stores.
The study's failure to show that the interventions made a difference in reducing the prevalence of overweight and obese children combined is not necessarily a negative, said Nicolas Stettler, an associate professor of pediatrics and epidemiology at Children's Hospital of Philadelphia. If societal rates are beginning to decline, as this research suggests, then that broad trend could have masked the effects of the interventions themselves, said Stettler, who was not involved with the study.
"A lot of schools are starting to change," he said. They are removing sodas, reducing fat, and adding fruits and vegetables - less intensive versions of this approach. "But we still have a problem," Stettler said, and now there is evidence for a possible solution.
Contact staff writer Don Sapatkin at 215-854-2617 or firstname.lastname@example.org.