Although restrained eating is believed to increase overeating and weight in the long term, the opposite has also been found: Heavy individuals are more likely to diet. The objective of the current study was to test both pathways for adolescents. A longitudinal model was used to explore the bidirectional associations between restrained eating and body mass index (BMI). At 3 annual waves, restrained eating and BMI were obtained from both older (M age 15.2 years old) and younger (M age 13.4 years old) adolescent boys and girls who were sibling pairs in 404 Dutch families. Structural equation modeling showed that BMI predicted restrained eating more consistently than the other way round. The results remained the same when analyzed by sex, age, socioeconomic status, and overeating tendency. Thus, in our general survey of adolescents restrained eating did not seem to be a successful weight loss strategy, nor did it consistently predict weight increase. Positive associations between restrained eating and BMI should mainly be interpreted in the sense that higher BMI predicted more restrained eating.