PROJECT SUMMARY South Asian is one of the fastest growing ethnic groups in the United States (US). The striking overweight and obesity prevalence (78%) among foreign-born South Asian American adults is a public health concern, as it affects not only their own health, but transgenerational obesity risks for SA American youth. Physical inactivity among South Asian American adults partly explains their high obesity risk. Despite the potential of elevated physical inactivity and obesity risks among South Asian American children, few studies evaluated physical activity and obesity among South Asian American children at a national level. Further, cultural factors, such as gender norm, among South Asian American families may discourage South Asian female youth to participate in physical activity. However, US data are lacking to understand how parents’ and child’s cultural factors influence the child’s physical activity behaviors among South Asian American families. To address these research gaps, the goals of this R03 project are to evaluate physical activity and body composition of South Asian American youth and to elucidate their cultural factors associated with physical activity behaviors. This R03 project proposes to conduct secondary data analyses to achieve two aims. Aim 1 is to evaluate physical activity and body composition among South Asian American youth using the 2011-Mar2020 National Health and Nutrition Examination Survey (NHANES) data. This evaluation will be conducted in comparison with other Asian (i.e., Chinese, Filipino) and racial/ethnic groups (i.e., Black, Hispanic, White). We will apply an innovative machine learning analytic method to estimate physical activity levels. Aim 2 is to examine the relationships between South Asian parents’ and daughters’ cultural factors and daughters’ physical activity using the baseline data of the South Asian Active Together (SAATH) clinical trial. This cost-efficient R03 project will produce high-impact knowledge, including a national evaluation of physical activity and body composition and the cultural determinants of physical activity behaviors among South Asian American youth. The outputs of the project will lay the foundation for designing an intervention for physical activity promotion of South Asian American youth. This project will also contribute to accelerating the adoption of the innovative machine learning analytic approach in physical activity research.