Body Mass Index vs Body Fat Percentage as a Predictor of Mortality in Adults Aged 20-49 Years

ABSTRACT PURPOSE Body mass index (BMI) is the current standard body composition measurement. We examined BMI vs body fat percentage (BF%) for 15-year mortality risk among adults aged 20-49 years. METHODS In this nationally representative cohort of US adults in the National Health and Nutrition Examination Survey, Cox proportional hazard regression was computed for 15-year mortality risk. Healthy and overweight/obese BMI were 18.5-24.9 and ≥25 kg/m2, respectively. The unhealthy BF% and waist circumference (WC) thresholds were ≥27% and ≥44%, and >40 and >35 inches, for men and women, respectively. The 15-year mortality risk for BMI, BF%, and WC was computed. RESULTS Body fat percentage and WC are both significantly associated with 15-year, allcause mortality (BF%: unadjusted hazard ratio HR 2.01; 95% CI, 1.45-2.78; P P P P = .009) and heart disease mortality (BF%: unadjusted HR 4.20; CI, 1.94-9.11; P P = .003; WC: unadjusted HR 4.75; CI, 2.45-9.21; P P CONCLUSION Body fat percentage is a better predictor of 15-year mortality risk factor in young adults than BMI. A move to using BF% rather than BMI may change how we measure body composition for risk stratification.