A longitudinal study was used to examine age differences in the role of body mass index (BMI) and sociocultural pressures in predicting changes in body image and strategies to both lose weight and increase muscles among 443 children aged between 8 and 12 years (207 boys, 236 girls) over a 16-month period. The strongest predictors of body image and these strategies were BMI, the media and mothers, and to a lesser extent fathers and best friends. Girls were focused on losing weight, whereas boys were focused on both increasing muscle and losing weight. Surprisingly, there was a reduction in strategies both to lose weight and increase muscles as children approached adolescence. The implications of these findings for preventative educational programs for boys and girls are discussed.