ABSTRACT. Objective. To assess the prevalence and correlates of products used to improve weight and shape among male and female adolescents.Methods. A cross-sectional study was conducted of 6212 girls and 4237 boys who were 12 to 18 years of age and enrolled in the ongoing Growing Up Today Study. The outcome measure was at least weekly use of any of the following products to improve appearance, muscle mass, or strength: protein powder or shakes, creatine, amino acids/hydroxy methylbutyrate (HMB), dehydroepiandrosterone, growth hormone, or anabolic/injectable steroids.Results. Approximately 4.7% of the boys and 1.6% of the girls used protein powder or shakes, creatine, amino acids/HMB, dehydroepiandrosterone, growth hormone, or anabolic/injectable steroids at least weekly to improve appearance or strength. In multivariate models, boys and girls who thought a lot about wanting more defined muscles (boys: odds ratio [OR]: 1.6; 95% confidence interval [CI]: 1.1-2.2; girls: OR: 2.3; 95% CI: 1.2-3.2) or were trying to gain weight (boys: OR: 3.0; 95% CI: 2.0 -4.6; girls: OR: 4.3; 95% CI: 1.6 -11.4) were more likely than their peers to use these products. In addition, boys who read men's, fashion, or health/fitness magazines (OR: 2.3; 95% CI: 1.1-4.9) and girls who were trying to look like women in the media (OR: 2.9; 95% CI: 1.4 -4.0) were significantly more likely than their peers to use products to improve appearance or strength, but hours per week watching television, watching sports on television, and participation in team sports were not independently associated with using products to improve appearance or muscle mass.Conclusions. Girls and boys who frequently thought about wanting toned or well-defined muscles were at increased risk for using potentially unhealthful products to enhance their physique. These results suggest that just as girls may resort to unhealthful means to achieve a low body weight, girls and boys may also resort to unhealthful means to achieve other desired physiques. A lthough weight concerns are less common among male than female individuals, recent data suggest that these concerns are becoming more prevalent. 1 Among female individuals, weight dissatisfaction increases with relative weight, but among male individuals, the relationship is more complicated. 2,3 For both male and female individuals, it is undesirable to be overweight, but for male individuals, it is also undesirable to be too lean or not sufficiently muscular. 2,4 Most of the research on body dissatisfaction has focused on a desire to be thin and the unhealthful methods that people, mainly female individuals, use to achieve that goal. 5,6 The prevalence of a desire to be more muscular and the prevalence of using unhealthful methods to increase muscle mass or definition are less well studied. 7 Most [8][9][10][11][12] but not all studies 13 have found that use of anabolic steroids, a substance known to aid in increasing muscle mass, is more common among male than female individuals. For example, in a large cross-sectional stud...