This study examined changes in extreme weight change attitudes and behaviors (exercise dependence, food supplements, drive for thinness, bulimia) among adolescent boys and girls over a 16 month period. It also investigated the impact of body mass index, puberty, body image, depression and positive affect on these attitudes and behaviors 16 months later. The participants were 847 young adolescents (411 boys, 436 girls). Participants completed questionnaires evaluating the above variables on three occasions, eight months apart. Girls obtained higher scores on exercise dependence, drive for thinness and bulimia. Changes in depression and body image importance were the strongest predictors of changes in these extreme attitudes and behaviors among boys; changes in depression, body dissatisfaction and body image importance were the strongest predictors for girls. The need for gender specific educational and intervention programs for adolescents are discussed.