The Relative Effects of Obesity and Insulin Resistance on Cardiovascular Risk Factors in Nondiabetic and Normotensive Men

BACKGROUND: Several reports have documented that Asians have a strong tendency to develop insulin resistance. The aims of this study were to evaluate the relative effects of insulin resistance and obesity on the risk factors for coronary heart disease (CHD) and to clarify whether insulin resistance accentuates these effects in apparently healthy men. METHODS: We conducted a cross sectional survey on 4,067 apparently healthy Korean men, aged between 20 and 83 years, with body mass indices (BMI) ranging from 15.19 to 40.29 kg/m(2). The presence of insulin resistance was defined as a homeostasis model assessment (HOMA-IR) value >2.23, which is the cutoff for the highest decile in the normal BMI group (BMI <23 kg/m(2); 1,438 subjects). RESULTS: The prevalence of insulin resistance was 24.7% in the overweight subjects (23≤BMI<25 kg/m(2); 1,259 subjects) and 43.9% in the obese subjects (BMI≥25 kg/m(2); 1,370 subjects). The BMI was identified as the major determinant for total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C), and waist circumference (WC) as the most important for apolipoprotein B (Apo B), systolic and diastolic blood pressures and C-reactive protein (CRP), and HOMA-IR as the most important for fasting blood sugar, triglyceride (TG), low high-density lipoprotein cholesterol (HDL-C), apolipoprotein A-I (Apo A-I) and TC/HDL ratio. The presence of insulin resistance was found to accentuate the risk factors for CHD, with the exception of LDL-C and Apo A-I in the obese. CONCLUSION: WC and HOMA-IR were found to be closely associated with non-traditional markers for CHD, such as high Apo B, hypertriglyceridaemia and the TC/HDL-C ratio, which are predictors for the presence of small, dense LDL particles. The insulin resistance among obese men was more prevalent than expected, and the presence of insulin resistance accentuates the effect of obesity in terms of the risk of CHD.