Insulin resistance, as expressed by HOMA-R, is strongly determined by waist circumference or body mass index among Japanese working men

Summary Objective This study was intended to identify significant determinant factors of insulin resistance. Methods Insulin resistance was assessed using the homeostasis model assessment for insulin resistance (HOMA-R) and was calculated as “Fasting plasma glucose × Fasting serum insulin)/405”. The target subjects were 3008 working men. The serum lipid profiles, uric acid level, insulin level, plasma glucose level, hemoglobin A1C level, and blood pressure, in addition to the waist circumference or body mass index, were also measured. A stepwise multiple regression analysis was performed using log-transformed values of HOMA-R as the dependent variable. Results The standardized regression coefficient for waist circumference was about six times larger than that for hemoglobin A1c (0.45 and 0.08, respectively). The standardized regression coefficients for the other factors were 0.15 for diastolic blood pressure, 0.10 for the low-density lipoprotein cholesterol level, −0.06 for age, −0.04 for habitual exercise, 0.14 for no habitual drinking, and 0.07 for no smoking. When body mass index was substituted for waist circumference, almost the same results were obtained. The adverse effects of no smoking and no habitual drinking on the HOMA-R score might be explained, at least in part, by the relation of these factors with obesity. Regular exercise had a protective effect on lowering insulin resistance. Conclusions A close relation exists between obesity-related indices (waist circumference and body mass index) and insulin resistance, independent of age and other vascular risk factors in Japanese working men.