Developmental Effects and Sex Differences in Physical Activity Level, Body Mass Index, and Body Image during Adolescence.

[[abstract]]The study was designed to investigate annual and sex differences in physical activity level, body mass index (BMI), and body image in adolescents. One hundred and sixty nine early adolescent students (81 males and 88 females) (average age 13.4±0.5 years of age) served as participants in the longitudinal study. Physical activity level questionnaires, body image perception questionnaire, and annual height and weight measurement were administered annually for three years. Pearson’s Product-Moment Correlation, Quadratic Regression Model, 3 (year) X 2 (sex) mixed design ANOVA, and 4 (BMI category) X 2 (sex) independent two-way ANOVA were used for statistical analyses. The findings were: (1) Physical activity level, physical appearance evaluation, and body areas satisfaction were positively correlated one another, however, no relationship was found between physical activity level and physical appearance orientation. (2) BMI was found not a predictor for physical activity level, physical appearance evaluation, physical appearance orientation in each year. But MBI was found a predictor for body areas satisfaction in both second and third year. (3) Physical activity level in female adolescents decreased as a function age, and male adolescents were higher than female adolescents in physical activity level in each year. (4) Male adolescents were higher in physical appearance evaluation and body areas satisfaction than their counterpart in all three years, and female adolescents showed decreased in physical appearance evaluation and body areas satisfaction with age. On the other hand, both female and male adolescents’ physical appearance orientation increased with age, and female adolescents were higher in physical appearance orientation than their counterpart in each year. (5) No sex differences were found with regards to physical activity level and BMI in adolescents. (6) Physical appearance evaluation and body areas satisfaction of those in appropriate, over-weight, and obesity BMI categories were higher for male adolescents than their counterpart. However, no difference was found between physical appearance orientation and various BMI categories.