Abstract P341: Physical Activity and Dual Energy X-ray Absorptiometry Measured Body Composition in Global Multi-Ethnic Cohorts

Background: Obesity is an important risk factor for the development of heart disease, and unfortunately rates of obesity have been growing worldwide. Obesity is often defined by body mass index (BMI) ≥30kg/m 2 , however, BMI cannot distinguish between fat or lean mass nor differences in fat distribution. Dual energy x-ray absorptiometry (DXA) provides more detailed measurements of body composition, but research assessing the association between physical activity and detailed body composition measures in diverse populations is lacking. This study therefore examined associations between physical activity and DXA-derived measures of adiposity in Chinese, Malay, Indian and White European adults from two large-scale prospective cohort studies. Methods: From 2006-2010, adults from the general population were recruited to both The Malaysian Cohort (TMC) study (N=119 555) and the UK Biobank (N=502 487). Physical activity was self-reported by questionnaire at baseline assessment and approximately 5-yearly resurveys in both cohorts. Between 2020-2023, 5489 participants underwent a DXA scan in TMC; while between 2014-2023, 60 280 participants had DXA scans in UK Biobank. Analyses excluded participants with missing data and prior diseases that may impact body composition. Multivariable linear regression (adjusted for demographic and lifestyle confounders) was used to examine associations between physical activity and body composition measures across ethnic groups, and estimates were corrected for regression dilution bias by using estimates of ‘usual physical activity’ derived from repeat measurements. Results: After exclusions, 1723 Chinese, 1245 Malay and 609 Indian participants were included in the TMC analyses and 56 758 White Europeans in the UK Biobank (mean age 57.1 years, 41.2% male in TMC and 54.7 years, 47.7% male in UK). In TMC, physical activity was not associated with BMI, however it was inversely associated with DXA adiposity measures and positively associated with lean mass. Comparing the highest quintile of physical activity to the lowest, total fat mass was 0.7 kg lower (95%CI: -1.1- -0.3) and total lean mass was 0.6 kg higher (0.3-0.9). There was no evidence of effect modification by ethnicity in TMC, but results in White Europeans were stronger: total fat mass was 3.9 kg lower (-4.1- -3.6) and lean mass was 1.2 kg higher (1.1-1.4) comparing the highest to lowest quintiles of physical activity. Interpretation: This is the first large-scale study to examine associations between physical activity and DXA-derived measures of body composition in multi-ethnic cohorts from Malaysia and the UK. The findings support physical activity interventions to reduce obesity-related disease across diverse populations and highlight the value of using detailed body composition measures.