Metabolically healthy obesity increased diabetes incidence in a middle-aged and elderly Chinese population

Background We examined the association between metabolically healthy obese (MHO) and diabetes incidence in a middle-aged and elderly population and whether the association differed by the presence of nonalcoholic fatty liver disease (NAFLD). Methods We examined 17 801 participants without diabetes at study entry (7980 males and 9821 females with a mean age of 63.2 years) derived from the Dongfeng-Tongji cohort study (median follow-up: 4.6 years). Participants were divided into six groups based on BMI (normal weight, overweight, or obese) and metabolic health (healthy/unhealthy) defined by the Adult Treatment Panel III criteria. The MHO was defined as BMI greater than 28.0 kg/m(2) with 0 or 1 of four metabolic abnormalities (elevated blood pressure, triglyceridaemia, hyperglycaemia, low HDL cholesterol). The hazard ratio (HR) and 95% confidence interval (CI) for incident diabetes were derived from the Cox proportional hazard regression model. Results During 79 843 person-years of follow-up, 1453 individuals developed diabetes. Compared with metabolically healthy normal weight (MH-NW) individuals, the multivariable-adjusted HRs (95% CI) were 1.74 (1.16-2.59) for MHO and 2.15 (1.65-2.81) for metabolically unhealthy obese subjects after adjusting for age, sex, smoking, alcohol drinking, physical activity, fruit and vegetable consumption, family history of diabetes, fasting glucose, waist circumference, and NAFLD. Among those without NAFLD, MHO individuals showed higher incidence of diabetes (multivariate-adjusted HR = 2.71, 95% CI: 1.47-5.00) than MH-NW individuals. Conclusions The MHO phenotype was associated with increased incidence of diabetes in a middle-aged and elderly population, and the association did not differ by the presence or absence of NAFLD.