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High fitness in adolescence is associated with higher subsequent academic achievement. The promotion of PA might benefit school performance because of enhanced fitness levels in the long-term and positive influences of PA in the shortterm. The association between weight status and educational attainment remains controversial.

The study investigated the effects of sedentary behavior (SB) on mental well-being and examined differences between screen-based (sSB) and non-screen-based sedentary behaviors (nSB) separately by gender. In a total sample of 1296 students (609 girls) aged 12 e17 (m ¼ 13.7, SD ¼ 0.67), SB, depressed affect, self-esteem, physical self-concept, general self-efficacy and physical activity were assessed through self-administered questionnaires. Among girls, lower scores in self-esteem, physical self-concept as well as general selfefficacy were associated with higher sSB but not nSB. Among boys higher levels of sSB related to higher self-esteem, nSB but not sSB predicted higher scores in depressed affect, and there was a u-shaped association between sSB and general self-efficacy. Results replicate the inverse association between SB and mental well-being, and suggest a distinction between nSB and sSB especially among girls. Additional studies will be necessary to replicate, and further examine mediating mechanisms.

Adolescents in modern societies spend about 3 h per day in front of small recreational screens. The present study aims at investigating the relationships between screen time and different indicators of overweight. In addition, associations with the self‐concept of physical attractiveness and perceived weight status will be examined. In a total sample of 1228 students (47.5% girls) aged 12–17 years (M = 13.74, SD = 0.68) cross‐sectional associations were determined by conducting multiple linear regression analyses. Screen time showed a significant positive dose–response relationship with body mass index percentile, waist circumference, body fat, waist‐to‐height‐ratio, and a negative association with self‐concept of physical attractiveness independent of age, gender and moderate to vigorous physical activity. Thus, screen time seems to be associated with adolescent overweight, abdominal obesity, and body dissatisfaction. Reducing adolescents' screen time could be a promising approach for primary prevention of obesity and for the promotion of a positive physical self‐concept.

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