The rise in preoccupation with weight and dieting among adolescent girls in the last 30 years has produced a plethora of clinical research on body image and other correlates of disordered eating. However, there have been few longitudinal population studies investigating precursors and prevalence of actual cognitive distortion in body image among girls or its health consequences. Data on U.S. girls (ages 12-21) were drawn from the National Longitudinal Study of Adolescent Health (Add Health). Using Symbolic Interaction and Feminist Sociocultural theories, logistic regressions were conducted to test theoretical propositions and investigate possible pathways of risk from gendered self-concept to body image distortion (BID), and from BID to risky weight loss behavior (e.g., diet pills, vomiting, and laxatives) and more common weight loss behaviors such as dieting and exercising to lose weight. Family social support, parent traditional attitudes, and background variables (race/ethnicity, age, parent education, and BMI status) were also considered. Multivariate analyses at Time 1 suggest that self-esteem is negatively associated with BID and high appearance investment is positively associated with BID. Multivariate longitudinal analyses suggest that BID at Time 1 predicts the onset of both risky weight loss behaviors and dieting by Time 2 (one year later), controlling for weight loss behavior at Time 1. High self-esteem is also associated with decreased risk of engaging in risky weight loss behaviors and decreased dieting behavior. Self-esteem has a direct effect on BID and an indirect effect on unhealthy weight loss behaviors, mediated through BID. There is no evidence that BID mediates the relationship between self-esteem and dieting to lose weight, however. Parent traditional attitudes are associated with girls' higher social passivity, but are unrelated to self-esteem and appearance investment. Results suggest that universal, developmentally appropriate prevention programs addressing body image, realistic body weight self-assessment, and self-esteem are needed, as well as targeted programs for girls at risk for BID or who already display BID, in order to curb risky and unnecessary weight loss practices. Suggestions for designing screening and prevention programs based on theory and current research are discussed.