Involvement in sport is the most widely reported organized activity among children and adolescents. To date, organized sports also represent the only organized activity examined in conjunction with youths\u27 eating behaviors. Organized sports serve as contexts where messages about healthy eating and body image are communicated, and adolescents\u27 beliefs about food and their bodies\u27 degree of thinness and muscularity has the potential to be amplified in such settings as youth strive to perform at high levels during athletic competitions. However, inconsistency in the measurement of both organized sports participation and adolescents\u27 engagement in problematic under- and over-eating behaviors has resulted in a more limited understanding of the developmental trajectories of both constructs during adolescence. Moreover, explanatory mechanisms, specifically adolescents\u27 belief systems about food and their bodies, may explain associations between sports involvement and problematic eating behaviors, and such associations may be especially prevalent for youth involved in multiple organized activities simultaneously (e.g., sports and church activities). Therefore, the goals of current study were threefold: (1) examine associations between multidimensional constructs of sports investment and problematic under- and over-eating behaviors, (2) examine explanatory associations between sports investment and problematic under- and over-eating behaviors through adolescents\u27 beliefs about food, and their bodies\u27 degree of thinness and muscularity, and (3) examine whether explanatory associations vary as a function of adolescents\u27 participation in additional organized activities simultaneously with sports. Participants included 610 adolescents (M = 15.93, SD = 1.10, Range = 14 -- 19 years, 58.6% female) who completed measures assessing participation in organized activities, athletic identity status, beliefs about thinness, muscularity, and under- and over-eating behaviors, and engagement in problematic under- and over-eating behaviors. Across all youth, sports investment was associated with binge eating and over-eating behaviors, and such associations were explained by beliefs about the body\u27s degree of muscularity. In addition, being highly invested in sports was associated with higher levels of moderate and severe under-eating behaviors through lower food autonomy of over-eating behaviors. Several significant gender differences also emerged. Sports investment was directly associated with binge eating for boys, while sports investment was indirectly associated with both under- and over-eating behaviors for girls. Finally, involvement in additional organized activities simultaneously with sports was associated with protective and adverse outcomes. Results indicate that church activities are a context promoting healthy eating habits, while participation in club-related activities may lead to increased scheduling demands, and a decreased focus on healthy eating patterns. Overall, these findings indicate that organized sports represent an important context contributing to adolescents\u27 conceptualizations of food-related behaviors and the body\u27s degree of muscularity and, as well differences in problematic under- and over-eating behaviors
