AbstractBackgroundThis study tested whether the dissonance-based Body Project eating disorder prevention program reduced onset of subthreshold/threshold anorexia nervosa (AN), bulimia nervosa (BN), binge eating disorder (BED), and purging disorder (PD) over long-term follow-up.MethodsData were combined from three prevention trials that targeted young women at high-risk for eating disorders (N = 1092; M age = 19.3). Participants were randomized to Body Project groups led by peer educators or expressive writing/educational controls and completed masked diagnostic interviews over 2- to 4-year follow-ups. Logistic regressions tested whether onset of each eating disorder over follow-up differed between Body Project and control participants.ResultsPeer-led Body Project groups produced a 46% reduction in onset of subthreshold/threshold BN and a 62% reduction in onset of PD relative to controls over follow-up. Rates of onset of subthreshold/threshold AN and BED did not significantly differ between peer-led Body Project participants and control participants.ConclusionsResults support the dissemination of the peer-led Body Project for reducing future onset of BN and PD. This study and recent research suggest that thin-ideal internalization, the risk factor for eating disorders targeted in the Body Project, may be more relevant for predicting onset of BN and PD compared to AN and BED. Findings support the development of a version of the Body Project aimed to reduce risk factors that have predicted future onset of all four types of eating disorders (e.g. overvaluation of weight/shape, fear of weight gain), which may more effectively prevent all eating disorder types.