Objective: To determine if adolescents who report dieting and different weight-control behaviors are at increased or decreased risk for gains in body mass index, overweight status, binge eating, extreme weight-control behaviors, and eating disorders 5 years later. Design: Population-based 5-year longitudinal study. Participants: Adolescents (N=2,516) from diverse ethnic and socioeconomic backgrounds who completed Project EAT (Eating Among Teens) surveys in 1999 (Time 1) and 2004 (Time 2). Main outcome measures: Weight status, binge eating, extreme weight control, and self-reported eating disorder. Statistical analysis: Multiple linear and logistic regressions. Results: Adolescents using unhealthful weight-control behaviors at Time 1 increased their body mass index by about 1 unit more than adolescents not using any weight-control behaviors and were at approximately three times greater risk for being overweight at Time 2 (odds ratio [OR]=2.7 for girls; OR=3.2 for boys). Adolescents using unhealthful weight-control behaviors were also at increased risk for binge eating with loss of control (OR=6.4 for girls; OR=5.9 for boys) and for extreme weight-control behaviors such as self-induced vomiting and use of diet pills, laxatives, and diuretics (OR=2.5 for girls; OR=4.8 for boys) 5 years later, compared with adolescents not using any weight-control behaviors. Conclusions: Dieting and unhealthful weight-control behaviors predict outcomes related to obesity and eating disorders 5 years later. A shift away from dieting and drastic weight-control measures toward the long-term implementation of healthful eating and physical activity behaviors is needed to prevent obesity and eating disorders in adolescents.