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Am Fam Physician. 2005;72(11):2342-2344

Eating disorders and disordered weight-control behaviors among adolescent girls are major public health concerns. These behaviors (e.g., self-induced vomiting, use of laxatives, diet pills) are associated with significant morbidity in this age group. The obesity epidemic also affects this age group. An adolescent who is obese is more likely to attempt weight control through self-induced vomiting and laxative use. Dieting, also a common strategy that adolescent girls use to control their weight, can lead to significant negative effects. Researchers are focusing on the link between eating disorders and obesity. Austin and colleagues evaluated how an obesity prevention program affected self-induced vomiting and laxative and diet pill use among adolescent girls trying to control weight.

The study included middle-school girls whose schools were randomized to receive intervention or no intervention (control group). The intervention group participated in Planet Health, which focuses on promoting healthful nutrition, increasing physical activity, and reducing television watching. Previous studies have shown that Planet Health reduced the risk of obesity in adolescent girls. In this study, participants completed a survey about dietary habits, physical activity, television viewing, dieting, self-induced vomiting, and laxative and diet pill use at baseline and at follow-up. Height, weight, and skinfold measurements also were obtained. Survey responses regarding self-induced vomiting, use of laxatives, and use of diet pills were combined to create a single disordered weight control behavior variable. Obesity was defined as a body mass index or triceps skinfold thickness above the 85th percentile for age and sex. The study was performed over two school years.

Final analysis included 480 girls with a mean age of 11.5 years. The control and intervention groups had similar percentages of participants who were obese and who were dieting at baseline. After the intervention, significantly fewer girls in the intervention group reported laxative or diet pill use compared with the control group. After controlling for ethnicity and control groups, the girls in the intervention group had less than one half the risk for laxative or diet pill use compared with the girls in the control group (odds ratio 0.41, 95% confidence interval 0.22 to 0.75). The intervention had a greater impact on girls who did not report dieting at baseline than on girls who did diet.

The authors conclude that school-based interventions may be effective in preventing obesity and disordered weight-control behaviors in adolescent girls. They estimate that 59 percent of new disordered weight-control behaviors might have been prevented if the girls in the control group participated in the intervention. This strategy provides an integrated, cost-effective approach to both disorders and could allow schools to address both in one prevention program.

editor’s note: The number of obese children has grown substantially over the past few years. Weight-control disorders are also a continuing problem for adolescents. Obesity prevention, however, may increase weight-control disorders. The Planet Health program was designed to concentrate on health habits and not weight reduction. In the study by Austin and colleagues, the intervention group did not show an increase in weight-control disorders after the intervention. Planet Health had a positive impact on girls but no impact on boys with regard to obesity prevention. In addition, the intervention had less of an impact on girls who had already tried dieting. This data is similar to a study concerning the Drug Abuse Resistance Education program, which showed that the program positively affected boys but not girls.1 The implication is that intervention coordinators need to consider sex differences when creating and implementing prevention programs.—k.e.m.

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