This study compared the abilities of body mass index (BMI) and waist circumference (WC) to identify resistance to insulin-mediated glucose uptake and related metabolic abnormalities in 261 apparently healthy patients. Insulin resistance and associated metabolic abnormalities occur more commonly in the overweight/obese, and these changes increase the risk of cardiovascular disease (CVD). Determining either their BMI or WC can identify patients more likely to experience the adverse effects of excess adiposity on CVD risk, and the relative clinical utility of these measurements is not clear. Therefore, insulin-mediated glucose uptake was quantified in 261 apparently healthy adults by determining the steady-state plasma glucose concentrations during the insulin suppression test; the higher the concentration, the greater the defect in insulin action. The fasting plasma glucose, triglyceride, and total, low-density lipoprotein, and high-density lipoprotein cholesterol concentrations were also measured, and the associations between these variables and the measurements of BMI and WC were determined. The greater the degree of adiposity, the higher the steady-state plasma glucose, fasting plasma glucose, and triglyceride concentrations, irrespective of the index of adiposity used. However, increases in the total and low-density lipoprotein cholesterol and decreases in the high-density lipoprotein cholesterol concentrations were only seen in those with higher BMI values. In conclusion, because BMI performed at least as well as WC in identifying differences in insulin sensitivity and multiple CVD risk factors, either estimate can be used to identify patients at increased CVD risk.