Physical Activity and Mortality Across Levels of Adiposity: A Prospective Cohort Study From the UK Biobank.

ABSTRACT

OBJECTIVE: To examine the combined and stratified associations of physical activity and adiposity measures, modelled as body mass index (BMI), abdominal adiposity (waist circumference), and body fat percentage (BF) with all-cause mortality. PATIENTS AND METHODS: Using the UK Biobank cohort, we extracted quintiles of self-reported weekly physical activity. Categories of measured BMI, waist circumference, and BF were generated. Joint associations between physical activity-adiposity categories and mortality were examined using Cox proportional hazards models adjusted for demographic, behavioral, and clinical covariates. Physical activity-mortality associations were also examined within adiposity strata. Participants were followed from baseline (2006 to 2010) through January 31, 2018. RESULTS: A total of 295,917 participants (median follow-up, 8.9 years, during which 6684 deaths occurred) were included. High physical activity was associated with lower risk of premature mortality in all strata of adiposity except for those with BMI ≥35 kg/m2. Highest risk (HR, 1.54; 95% CI; 1.33 to 1.79) was observed in individuals with low physical activity and high BF as compared with the high physical activity-low BF referent. High physical activity attenuated the risk of high adiposity when using BF (HR, 1.24; 95% CI; 1.04 to 1.49), but the association was weaker with BMI (HR, 1.45; 95% CI; 1.21 to 1.73). Physical activity also attenuated the association between mortality and high waist circumference. CONCLUSION: Low physical activity and adiposity were both associated with a higher risk of premature mortality, but high physical activity attenuated the increased risk with adiposity irrespective of adiposity metric, except in those with a BMI ≥35 kg/m2.