Body Mass Index vs Body Fat Percentage as a Predictor of Mortality in Adults Aged 20-49 Years
Arch G. Mainous, Lu Yin, Velyn Wu, Pooja Sharma, Breana M. Jenkins, Aaron Saguil, Danielle S. Nelson, Frank A. Orlando
Abstract
<h3>ABSTRACT</h3> <h3>PURPOSE</h3> 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. <h3>METHODS</h3> 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/m<sup>2</sup>, 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. <h3>RESULTS</h3> 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; <i>P</i> < .001; adjusted HR 1.78; CI, 1.28-2.47; <i>P</i> < .001; WC: unadjusted HR 1.94; CI, 1.38-2.72; <i>P</i> < .001; adjusted HR 1.59; CI, 1.12-2.26; <i>P</i> = .009) and heart disease mortality (BF%: unadjusted HR 4.20; CI, 1.94-9.11; <i>P</i> < .001; adjusted HR 3.62; CI, 1.55-8.45; <i>P</i> = .003; WC: unadjusted HR 4.75; CI, 2.45-9.21; <i>P</i> < .001; adjusted HR 4.01; CI, 1.94-8.27; <i>P</i> < .001). Body mass index has no statistically significant relationship with all-cause mortality. Body mass index has a significant association with heart disease mortality in the unadjusted model but not in the adjusted model. <h3>CONCLUSION</h3> 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.