Concerns about body image might prevent adolescents from participating in physical education (PE) classes and physical activities during leisure-time. In this cross-sectional study, we assessed the relationships between teacher support of autonomy, student motivations for PE, and positive body image, in a sample of Lithuanian adolescents. A total of 715 adolescents (51.89% girls) participated in the study. Ages ranged from 14 to 18 years, with a mean age of 16.00 (SD = 0.79) for girls and 15.99 (SD = 0.75) for boys. The questionnaire consisted of demographic questions, the Learning Climate Questionnaire, the Revised Perceived Locus of Causality in Physical Education Questionnaire, the Body Appreciation Scale-2, the Self-Report Habit Index for Physical Activity (PA), perceived physical fitness (PPF), and Godin Leisure-Time Exercise Questionnaire. The results showed that teacher support for students' autonomy was associated with higher positive body image. In adolescent girls, autonomous motivation for PE was the mediator between teacher support of autonomy and positive body image. The associations between self-determined motivation in PE and positive body image were mediated by PPF on one hand, and through PA habits and PPF on the other hand of the structural equation model (in girls). PA habits moderated associations between PE motivation and PPF. Associations between PE motivation and PPF were stronger in girls with the lowest PA habits compared to girls with mean PA habits. These results suggest that PE classes are important for promoting students' positive body images. PE teachers are advised to use pedagogical strategies that promote the self-determined motivation of students for PE. Increased self-determined motivation for physical education might be an effective strategy for physical self-perception and positive body image promotion in adolescent girls, especially those with low PA habits.
Keywords: adolescents; body appreciation; habits; physical activity; physical education classes; self-determination; support of autonomy.