OBJECTIVE: We wanted to determine whether obesity, abdominal fat distribution, and physical inactivity act similarly and independently as risk factors for noninsulin-dependent diabetes mellitus (NIDDM) and impaired glucose tolerance (IGT) in Hindu and Muslim Asian Indians, African-origin Creoles, and Chinese Mauritians. RESEARCH DESIGN AND METHODS: We examined a population-based random cluster sample of 5080 adult subjects from the Indian Ocean island of Mauritius. Glucose tolerance was assessed with a 75-g oral glucose tolerance test and World Health Organization criteria. RESULTS: Univariate data and multiple logistic regression models indicated that age, family history of diabetes, body mass index (BMI), waist-hip ratio (WHR), and physical inactivity conveyed similar risk for NIDDM (and IGT) in each ethnic group. After adjusting for all other factors, Hindu ethnicity conferred additional risk for NIDDM (but not IGT) in men, but in women there were no clear ethnic differences. Although BMI and WHR were independently significant risk factors, WHR conveyed relatively stronger risk for NIDDM than BMI in women, whereas the converse was true in men. For ethnic groups combined, the independent odds ratios for IGT associated with moderate and low physical activity scores (relative to high) were 1.56 and 1.71 (P less than 0.05), respectively, in men and 1.32 and 1.69 (P less than 0.05) in women. In subjects with asymptomatic NIDDM diagnosed during the survey, the independent odds ratios were 1.96 and 2.00 (P less than 0.05) in men and 1.73 and 2.70 (P less than 0.05) in women. CONCLUSIONS: These data indicate that BMI, abdominally distributed fat, and physical inactivity are important independent risk factors for both IGT and NIDDM in diverse ethnic groups. Attributable risk fractions for Mauritius suggest that populationwide modification of levels of these risk factors could potentially result in substantially lower occurrence of NIDDM (and IGT). Such interventions should be attempted in high-risk populations.