New evidence suggests that individuals with normal weight at diagnosis of type 2 diabetes (T2D) are at higher risk for all-cause mortality than those who were overweight or obese at diagnosis. While investigation of the determinants of different diabetes risk categories among those with obesity has become more common, explanations beyond genetic predisposition for the heterogeneity in risk among those without obesity are lacking. We hypothesized that visceral fat and insulin resistance would be associated with incident metabolic syndrome (MetS) and T2D among African American individuals with normal weight.
In 1,032 participants of the Jackson Heart Study with normal weight (BMI 18.5 – 24.9 kg/m2), we used logistic regression to investigate the determinants of incident MetS and T2D, separately. T2D and MetS were assessed at study visit 3 for the CT scan variables, and visits 2 and 3 for all other variables. We used the harmonized International Diabetes Federation criteria to define MetS. We excluded participants with prevalent MetS or T2D, and those with missing exposure or outcome data.
Normal weight participants with MetS or T2D were more likely to be older, male, have lower socioeconomic status, caloric, fiber, saturated fat intake, and higher CRP and visceral fat. Higher HOMA-IR and subcutaneous fat were seen only in those with MetS. Higher visceral fat, subcutaneous fat, BMI, and HOMA-IR were significantly associated with incident MetS after adjustment for age, sex, education, and income (Figure). Only visceral fat and HOMA-IR were significantly associated with incident T2D. Estimates for BMI, but not visceral fat, were strongly attenuated with mutual adjustment. Physical activity was not associated with MetS or T2D in any model.
In conclusion, visceral fat is more strongly associated with incident MetS and T2D than subcutaneous fat or physical activity, even in normal weight individuals, suggesting that
adiposity plays a role in the development of cardiometabolic dysfunction even in the absence of obesity.