Background: Cross-sectional research has found that dieting during adolesence and the use of extreme weight control behaviors are related to less healthful dietary patterns; however, little is known regarding longitudinal relationships. Objective: To describe patterns of weight control behavior over 5 years and examine relationships with nutritional outcomes in adolescents and young adults. Design: Population-based, longitudinal study in Minnesota. Youth completed Time 1 surveys in 1998-1999, and Time 2 surveys were completed in 2003-2004. Subjects/setting: The Project EAT (Eating Among Teens) survey and the Youth and Adolescent Food Frequency Questionnaire were completed by 1,242 females and 1,007 males in school classrooms at Time 1 and by mail at Time 2. Outcome measures and statistical analyses performed: Generalized linear modeling was used to predict each Time 2 outcome of interest (ie, meal and snack frequencies and dietary intake) across patterns of healthful and unhealthful weight control behavior (ie, never-engaging, stopping, starting, and persisting). Results: Approximately 45% of females and 17% of males reported persistent use of unhealthful weight control behaviors at both time points. Persisting to use only healthful weight control behaviors was reported by 10% of females and 15% of males. Among females, persistent use of unhealthful weight control behavior was associated (P<0.05) with measures of poorer dietary intake (eg, lower intakes of calcium and vegetables) and less frequent meals, whereas persistent use of healthful weight control behavior was associated with measures (P<0.05) of better dietary intake (eg, less fast food and fewer sugar-sweetened drinks). Among males, few associations were observed between dietary intake and either unhealthful or healthful weight control behavior. Conclusions: Health professionals should guide youth who have weight concerns by encouraging healthful eating habits to achieve or maintain appropriate weight and nutrition goals.