Independent Impact of Body Mass Index and Metabolic Syndrome on the Risk of Type 2 Diabetes in Koreans

Background: Although obesity and metabolic syndrome have been associated with the risk of type 2 diabetes mellitus (T2DM), it is unclear whether obese or overweight people without metabolic syndrome are at increased risk for T2DM. Methods: Clinical and laboratory data were assessed in 8,748 subjects without diabetes (5,707 men, 3,041 women; age 20-79 years) who underwent voluntary medical check-ups at a 5-year interval. The subjects were categorized by body mass index (BMI) and metabolic syndrome status at baseline, and the incidence of diabetes over 5 years was assessed. Results: Of the 8,748 subjects, 308 (3.5%) developed T2DM over 5 years. Compared with normal weight (BMI <25.0 kg/m(2)) individuals without metabolic syndrome, the adjusted odds ratios (ORs) were 1.61 (1.13-2.29) and 4.93 (1.90-12.79) for overweight (BMI 25.0-29.9 kg/m(2)) and obese (BMI 30.0 kg/m(2)) individuals without metabolic syndrome, respectively, and 6.94 (5.08-9.47) and 10.61 (5.59-20.14) for overweight and obese individuals with metabolic syndrome, respectively. Using the lower BMI cutoff points for Asian populations, compared with subjects with BMI <23 kg/m(2) without metabolic syndrome, the adjusted ORs for subjects with BMI 23-27.4 kg/m(2) and BMI 27.5 kg/m(2) without metabolic syndrome were 2.64 (1.74-4.00) and 4.31 (2.36-7.86), respectively, and 10.11 (6.53-15.67) and 16.69 (10.40-26.77), respectively, for those with metabolic syndrome. Conclusions: Overweight/obesity and metabolic syndrome both are significant risk factors for development of T2DM in Koreans, and overweight or obesity without metabolic syndrome should not be considered a harmless condition. The lower BMI cutoffs for Asian populations can be useful in predicting risk of T2DM in Koreans.