The impact of a school-based obesity prevention trial on disordered weight-control behaviors in early adolescent girls

Objective: To assess the impact of an obesity prevention intervention on use of self-induced vomiting/ laxatives (purging) and diet pills to control weight in girls in early adolescence. Design: We matched and randomly assigned 10 middle schools to an intervention or a control condition in a randomized controlled trial. Longitudinal multivariable analyses using generalized estimating equations were conducted with data from 480 girls to examine the effects of the intervention on the risk of reporting a new case of purging or diet pill use to control weight at follow-up 21 months later, while controlling for ethnicity and school matched pairs. Girls who reported purging or using diet pills at baseline were excluded from analyses. Setting: Middle schools. Participants: Four hundred eighty girls in early adolescence aged 10 to 14 years (mean age, 11.5 years). Intervention: The Planet Health obesity prevention program was implemented during 2 school years and was designed to promote healthful nutrition and physical activity and to reduce television viewing. Results: After the intervention, we found 14 (6.2%) of 226 girls in control schools and 7 (2.8%) of 254 girls in intervention schools reported purging or using diet pills to control their weight (P =.003). In a multivariable generalized estimating equation model, girls in intervention schools were less than half as likely to report purging or using diet pills at follow-up compared with girls in control schools (odds ratio, 0.41; 95% confidence interval, 0.22-0.75). Outcome: Reduced risk of using self-induced vomiting/ laxatives or diet pills to control weight in the past 30 days. Conclusion: These findings provide promising evidence that school-based interventions may effectively integrate prevention of both obesity and disordered weightcontrol behaviors.