BMI–Mortality Paradox and Fitness in African American and Caucasian Men With Type 2 Diabetes

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Abstract
OBJECTIVE: To assess the association between BMI, fitness, and mortality in African American and Caucasian men with type 2 diabetes and to explore racial differences in this association. RESEARCH DESIGN AND METHODS: We used prospective observational data from Veterans Affairs Medical Centers in Washington, DC, and Palo Alto, California. Our cohort (N = 4,156; mean age 60 ± 10.3 years) consisted of 2,013 African Americans (mean age, 59.5 ± 9.9 years), 2,000 Caucasians (mean age, 60.8 ± 10.5 years), and 143 of unknown race/ethnicity. BMI, cardiac risk factors, medications, and peak exercise capacity in metabolic equivalents (METs) were assessed during 1986 and 2010. All-cause mortality was assessed across BMI and fitness categories. RESULTS: There were 1,074 deaths during a median follow-up period of 7.5 years. A paradoxic BMI–mortality association was observed, with significantly higher risk among those with a BMI between 18.5 and 24.9 kg/m2 (hazard ratio [HR] 1.70 [95% CI 1.36–2.1]) compared with the obese category (BMI ≥35 kg/m2). This association was accentuated in African Americans (HR 1.95 [95% CI 1.44–2.63]) versus Caucasians (HR 1.53 [1.0–2.1]). The fitness–mortality risk association for the entire cohort and within BMI categories was inverse, independent, and graded. Mortality risks were 12% lower for each 1-MET increase in exercise capacity, and ∼35–55% lower for those with an exercise capacity >5 METs compared with the least fit (≤5 METs). CONCLUSIONS: A paradoxic BMI–mortality risk association was observed in African American and Caucasian patients with diabetes. The exercise capacity–mortality risk association was inverse, independent, and graded in all BMI categories but was more potent in those with a BMI ≥25 kg/m2.