Dieting and unhealthy weight control behaviors during adolescence: associations with 10-year changes in body mass index.

BACKGROUND Dieting and unhealthy weight control behaviors are common among adolescents and questions exist regarding their long-term effect on weight status. OBJECTIVE To examine 10-year longitudinal associations between dieting and unhealthy weight control behaviors and changes in body mass index (BMI) from adolescence to young adulthood. METHODS AND PROCEDURES A diverse population-based sample of middle school and high school adolescents participating in Project EAT (Eating and Activity in Teens and Young Adults) was followed up for 10 years. Participants (N = 1,902) completed surveys in 1998-1999 (Project EAT-I), 2003-2004 (Project EAT-II), and 2008-2009 (Project EAT-III). Dieting and unhealthy weight control behaviors at Time 1 and Time 2 were used to predict 10-year changes in BMI at Time 3, adjusting for sociodemographic characteristics and Time 1 BMI. RESULTS Dieting and unhealthy weight control behaviors at both Time 1 and Time 2 predicted greater BMI increases at Time 3 in males and females, as compared with no use of these behaviors. For example, females using unhealthy weight control behaviors at both Time 1 and Time 2 increased their BMI by 4.63 units as compared with 2.29 units in females not using these behaviors (p < .001). Associations were found in both overweight and nonoverweight respondents. Specific weight control behaviors at Time 1 that predicted larger BMI increases at Time 3 included skipping meals and reporting eating very little (females and males), use of food substitutes (males), and use of diet pills (females). CONCLUSIONS Findings clearly indicate that dieting and unhealthy weight control behaviors, as reported by adolescents, predict significant weight gain over time.