OBJECTIVE -We investigated the link between lipid-rich skeletal muscle, namely lowdensity muscle, and insulin resistance in Korea.RESEARCH DESIGN AND METHODS -Abdominal adipose tissue areas and midthigh skeletal muscle areas of 75 obese nondiabetic subjects (23 men, 52 women; mean age Ϯ SD, 41.9 Ϯ 14.1 years) were measured by computed tomography (CT). The midthigh skeletal muscle areas were subdivided into low-density muscle (0 to ϩ30 Hounsfield units) and normal-density muscle (ϩ31 to ϩ100 Hounsfield units). The homeostasis model assessment (HOMA) score was calculated to assess whole-body insulin sensitivity.RESULTS -The abdominal visceral fat area and the midthigh low-density muscle area were found to be well correlated with the HOMA score (r ϭ 0.471, P Ͻ 0.01 and r ϭ 0.513, P Ͻ 0.01, respectively). The correlation between low-density muscle area and insulin resistance persisted after adjusting for BMI or total body fat mass (r ϭ 0.451, P Ͻ 0.01 and r ϭ 0.522, P Ͻ 0.01, respectively) and even after adjusting for abdominal visceral fat area (r ϭ 0.399, P Ͻ 0.01).CONCLUSIONS -The midthigh low-density muscle area seems to be a reliable determinant of insulin resistance in Korean obese nondiabetic patients. Diabetes Care 26:1825-1830, 2003T he close relationship between abdominal adiposity and insulin resistance has been described in previous studies (1-3). Moreover, visceral adipose tissue is well recognized to be significantly related to insulin resistance of obese type 2 diabetic patients and even patients with normal weight (4,5).Recently, the role of intramuscular lipid components in insulin resistance became the subject of attention (6 -8). Lowdensity muscle represents lipid-rich skeletal muscle, which includes fat components between and inside the muscle fibers. Many other studies have already shown that low-density muscle is significantly related to insulin resistance in obese type 2 diabetic patients. However, this relation has not been investigated in Korea, where the prevalence of both obesity and diabetes is relatively low. Therefore, the current study was undertaken to investigate the potential link between low-density muscle and insulin resistance in the Korean population. RESEARCH DESIGN AND METHODS SubjectsA total of 75 subjects (23 men, 52 women; mean age Ϯ SD, 41.9 Ϯ 14.1 years) with sedentary lifestyle were enrolled in this cross-sectional study. Of these, 69 patients were obese (BMI Ͼ25 kg/m 2 ) and the remainder were overweight (BMI 23-25 kg/m 2 ), according to the revised definition of adult obesity in the AsianPacific race proposed at the Hong Kong meeting (9). A total of 33 premenopausal women and 19 women with natural menopause (mean age Ϯ SD, 31.2 Ϯ 7.8 and 54.8 Ϯ 7.9 years, respectively) were included. Subjects were divided into a normal glucose tolerance group (n ϭ 46) and an impaired glucose tolerance group (n ϭ 29), according to the results of an oral glucose tolerance test (OGTT). Individuals with a history of or evidence of hypertension, any type of diabetes, or cardiovascular disea...