Introduction Physical activity and sedentary time, along with other health-related behaviors, are influenced by various environmental factors. This study examines the associations of family, social, and built environments with physical activity and sedentary time in adolescents. Methods Participants aged 10–16 years were enrolled, with data from 308 adolescents analyzed. Physical activity and sedentary time were assessed using accelerometers, while family, social, and built environments were evaluated through questionnaires completed by parents/guardians. General Linear Models were used to examine associations between environmental factors and physical activity and sedentary time, adjusting for covariates. Results On average, participants engaged in 27.7 min of moderate-to-vigorous physical activity, 232.8 min of light physical activity, took 6,800 steps, and spent 595.4 minutes in sedentary time per day, with only 10% meeting the recommended 60 min of moderate-to-vigorous physical activity. Higher family support was associated with more moderate-to-vigorous physical activity ( β = 5.2), more light physical activity ( β = 7.9), more steps per day ( β = 688), and less sedentary time ( β = −13.2) per additional unit of family support. The social environment total score was not associated with physical activity or sedentary time. However, when analyzing individual components, social cohesion was negatively associated with physical activity and positively associated with sedentary time, while social control showed no significant relationship. No associations were found between the built environment and physical activity or sedentary time. Conclusions This study highlights the significant role of family support in promoting physical activity and reducing sedentary time in adolescents, with the family environment showing the strongest associations. In contrast, the social and built environments had limited influence on physical activity behaviors. The findings underscore the importance of family-based strategies to encourage active lifestyles. Clinical Trials Registration # NCT02784509.
Suárez-Reyes et al. (Thu,) studied this question.