Joint associations of physical activity and sedentary time with adiposity during adolescence: ALSPAC

Background In developing evidence-based physical activity (PA) guidelines for youth, a knowledge gap exists regarding the health effects of sedentary time (SED). The aim of this study was to determine the joint associations of moderate- and vigorous-intensity PA (MVPA) and SED with adiposity during adolescence. Methods The study sample was 2619 non-obese participants (56.7% female) from the UK Avon Longitudinal Study of Parents and Children. Accelerometer-measured MVPA and SED at age 11, 13, 15 years and self-reported TV viewing at age 13 and 16 years were used to create two exposure variables: six MVPA&SED combinations based on two MVPA patterns [>= 60 (active) and <60 min/day (inactive)] and three SED patterns [approximate to 25 (low), approximate to 30 (middle) and approximate to 35 min/h (high)] and six MVPA&TV combinations based on two MVPA patterns and three TV viewing patterns [<1-2 (low), 1-2 (middle) and >1-2 h/day (high)]. Adiposity was evaluated using fat mass index (FMI) at age 17 years. Results SED was not significantly associated with FMI in either active or inactive adolescents. However, higher TV viewing was associated with higher FMI in both active [adjusted FMI = 4.53 vs. 5.09 (95% CI = 4.87, 5.33) for low TV vs. high TV] and inactive adolescents [adjusted FMI = 4.91 vs. 5.21 (95% CI = 5.02, 5.39) for low TV vs. high TV]. Conclusions Higher TV viewing time, but not total SED, was prospectively associated with higher adiposity among both active and inactive adolescents, suggesting a specific sedentary behavior target for public health.