Ethnicity-specific BMI cutoffs for obesity based on type 2 diabetes risk in England: a population-based cohort study

Background National and global recommendations for BMI cutoffs to trigger action to prevent obesity-related complications like type 2 diabetes among non-White populations are questionable. We aimed to prospectively identify ethnicity-specific BMI cutoffs for obesity based on the risk of type 2 diabetes that are risk-equivalent to the BMI cutoff for obesity among White populations (>= 30 kg/m(2)). Methods In this population-based cohort study, we used electronic health records across primary care (Clinical Practice Research Datalink) linked to secondary care records (Hospital Episodes Statistics) from a network of general practitioner practices in England. Eligible participants were aged 18 years or older, without any past or current diagnosis of type 2 diabetes, had a BMI of 15.0-50.0 kg/m(2) and complete ethnicity data, were registered with a general practitioner practice in England at any point between Sept 1, 1990, and Dec 1, 2018, and had at least 1 year of follow-up data. Patients with type 2 diabetes were identified by use of a CALIBER phenotyping algorithm. Self-reported ethnicity was collapsed into five main categories. Age-adjusted and sex-adjusted negative binomial regression models, with fractional polynomials for BMI, were fitted with incident type 2 diabetes and ethnicity data. Findings 1 472 819 people were included in our study, of whom 1 333 816 (90.6%) were White, 75 956 (5.2%) were south Asian, 49 349 (3.4%) were Black, 10 934 (0.7%) were Chinese, and 2764 (0.2%) were Arab. After a median follow-up of 6.5 years (IQR 3.2-11.2), 97 823 (6.6%) of 1 472 819 individuals were diagnosed with type 2 diabetes. For the equivalent age-adjusted and sex-adjusted incidence of type 2 diabetes at a BMI of 30.0 kg/m(2) in White populations, the BMI cutoffs were 23.9 kg/m(2) (95% CI 23.6-24.0) in south Asian populations, 28.1 kg/m(2) (28.0-28.4) in Black populations, 26.9 kg/m(2) (26.7-27.2) in Chinese populations, and 26.6 kg/m(2) (26.5-27.0) in Arab populations. Interpretation Revisions of ethnicity-specific BMI cutoffs are needed to ensure that minority ethnic populations are provided with appropriate clinical surveillance to optimise the prevention, early diagnosis, and timely management of type 2 diabetes. Funding National Institute for Health Research. Copyright (C) 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license.

Automated summary

This study aimed to identify ethnicity-specific BMI cutoffs for obesity to prevent type 2 diabetes among non-White populations. The findings suggest that different ethnic populations have different BMI cutoffs equivalent to the risk of type 2 diabetes at a BMI of 30.0 kg/m(2) in White populations, highlighting the need for appropriate clinical surveillance for minority ethnic populations to optimize prevention and management of type 2 diabetes.