Obesity, weight change and diabetes risk in Black and White United States adults.

Abstract

Obesity and centralized fat distribution increase risk of type 2 diabetes. However, differences in the prevalence of these risk factors do not explain the excess diabetes in Black Americans. We used data from the NHANES I follow-up study (1971-1992) to investigate whether race (Black:White) modifies the effects of obesity (measured as body mass index, BMI), centralized fat distribution (measured by subscapular-to-triceps skinfold ratio, STR), and annual weight change (over 10 years, AWC), on diabetes risk; and whether AWC increases diabetes risk in already-obese adults (BMI $\ge$ 27.3 women, BMI $\ge$ 27.8, men). Of 11,383 non-diabetic Black and White subjects, 1,139 developed diabetes during 20 years of follow-up, as identified from self-report, hospital records, and death certificates. The association between BMI and diabetes risk was modified by race in both genders. In sex-specific logistic regression analyses, increased diabetes risk in Blacks was most evident in those with lower BMI. The association between STR and diabetes risk was similar across race. Of 7,696 subjects who were non-diabetic between baseline and first follow-up and who provided two weight measurements, 439 developed diabetes in the subsequent 10 years. Relative to weight-stable individuals, weight-gainers had increased diabetes risk. This association was modified by race only in men, with Black men at higher AWC-associated diabetes risk. Finally, of the 1,918 obese subjects who were non-diabetic between baseline and first follow-up, and who provided two weight measurements, 248 developed diabetes in the subsequent 10 years. Increased AWC predicted future diabetes in these subjects. Importantly, obese subjects who lost weight had lower risk of future diabetes. Our results indicate that the impact of BMI and AWC on diabetes risk may be greater among Blacks than Whites, and that obese individuals, regardless of race, experience added diabetes risk following weight gain and reduced risk following weight loss. These findings reinforce the association between baseline adiposity and risk of diabetes, and the importance of additional weight gain and weight loss in already-obese individuals. The effect of adiposity appears to be quantitatively different in Blacks and Whites. Further studies are needed to determine whether genetic and/or lifestyle differences explain the race effect.