A study done by University of Glasgow compared the relationship between adiposity and prevalent diabetes across ethnic groups in the UK Biobank cohort to derive ethnic-specific obesity cutoffs that equate to those developed on white populations in terms of diabetes prevalence. Compared to Western population, South Asians are prone to develop diabetes and its complications even at normal body weight.

UK Biobank recruited 502,682 U.K. residents aged 40–69 years, and used baseline data on the 490,288 participants from the four largest ethnic subgroups: 471,174 (96.1%) white, 9,631 (2.0%) South Asian, 7,949 (1.6%) black, and 1,534 (0.3%) Chinese. Regression models were developed for the association between anthropometric measures (BMI, waist circumference, percentage body fat, and waist-to-hip ratio) and prevalent diabetes, stratified by sex and adjusted for age, physical activity, socioeconomic status, and heart disease.

The results indicate that non white participants were two- to fourfold more likely to have diabetes. For the equivalent prevalence of diabetes at 30 kg/m2 in white participants, BMI equated to the following: South Asians, 22.0 kg/m2; black, 26.0 kg/m2; Chinese women, 24.0 kg/m2; and Chinese men, 26.0 kg/m2. Among women, a waist circumference of 88 cm in the white subgroup equated to the following: South Asians, 70 cm; black, 79 cm; and Chinese, 74 cm. Among men, a waist circumference of 102 cm equated to 79, 88, and 88 cm for South Asian, black, and Chinese participants, respectively.

It can be concluded that obesity should be defined at lower thresholds in nonwhite populations to ensure that interventions are targeted equitably based on equivalent diabetes prevalence. Furthermore, within the Asian population, a substantially lower obesity threshold should be applied to South Asian compared with Chinese groups.