The Associations Between Self-Perceived Actual and Ideal Body Sizes and Physical Activity Among Early Adolescents

Purpose : This study examined the association between self-perceived actual and ideal body sizes and objectively assessed moderate-to-vigorous physical activity (MVPA) among adolescents, controlling for puberty, fat mass index, and sex. A secondary objective was to explore the association between objectively assessed fat mass index and MVPA. Methods : Participants were 438 early adolescents ( M age = 11.61, SD = 0.92). Participants selected body sizes that represented their self-perceived actual and ideal bodies. Participants then wore an accelerometer for 1 week to assess MVPA. Polynomial regression analysis with response surface methods was used to explore MVPA in relation to the discrepancy and agreement (ie, no discrepancy) between self-perceived actual and ideal body sizes. Results : When self-perceived actual and ideal body sizes were in agreement and represented smaller and larger bodies, MVPA was low. Participants with similar self-perceived actual and ideal bodies in the middle of the body-size spectrum demonstrated the highest levels of MVPA. The direction and degree of the discrepancy between self-perceived actual and ideal bodies were not significantly associated with MVPA. Fat mass index was significantly and negatively associated with MVPA. Conclusions : These findings may inform physical activity promotion programs and provide methodological contributions to the study of how body image and MVPA are related.