Understanding the High Prevalence of Diabetes in U.S. South Asians Compared with Four Racial/Ethnic Groups: The MASALA and MESA Studies. We compared South Asians with four other race/ethnic groups in the U.S. to determine whether sociodemographic, lifestyle, or metabolic factors could explain the higher diabetes prevalence, and whether insulin resistance and β-cell dysfunction occurred at younger ages and/or lower adiposity levels compared with other groups. Cross-sectional analysis of two community-based cohorts, the Mediators of Atherosclerosis in South Asians Living in America (MASALA) study and the Multi-Ethnic Study of Atherosclerosis (MESA); all participants had no known cardiovascular disease and were between 44 and 84 years of age. We compared 799 South Asians with 2,611 whites, 1,879 African Americans, 1,493 Latinos, and 801 Chinese Americans. Type 2 diabetes was classified by fasting plasma glucose ≥126 mg/dL or use of a diabetes medication. Insulin resistance was estimated by the homeostasis model assessment (HOMA) and β-cell function was measured by the HOMA-β model.