New ethnicity-specific BMI cutoffs are needed because people of Indian, Chinese and Arab background are at risk of type 2 diabetes at much lower BMI values than the current cutoffs for obesity in Europeans, researchers say.
When compared to the current BMI cuttoff for obesity of 30 kg/m2 in white populations, the trigger for action on T2D risk should be 23·9 in south Asian populations, 26·9 in Chinese populations, and 26·6 in Arab populations, according to a UK study published in Lancet Diabetes and Endocrinology.
Researchers from Oxford University analysed data from almost 1.5 million UK residents of different ethnic background to calculated the risk of type 2 diabetes in relation to obesity.
After a median follow-up of 6·5 years 6·6% of the study population were diagnosed with type 2 diabetes.
After adjusting for age and sex, they found significantly lower BMI cutoffs for an equivalent incidence of type 2 diabetes in South Asian (23·9 kg/m2), Black (28·1 kg/m2), Chinese (26·9 kg/m2), and Arab (26·6 kg/m2) populations.
They noted that groups such as WHO currently recommend a BMI cutoff of 27·5 kg/m2 to define obesity in south Asian and Chinese populations to trigger lifestyle interventions, and the UK advisory group NICE also suggest that this lower BMI threshold should be used to trigger action to prevent type 2 diabetes among Black populations.
“Our study clearly showed that, compared with the risk of developing type 2 diabetes at a BMI of 30·0 kg/m2 in White populations, the equivalent risk among south Asian individuals occurred at a BMI of 23·9 kg/m2, a cutoff much lower than the recommended ethnicity-specific cutoff of 27·5 kg/m2,” they noted.
They also noted that previous attempts to define ethnicity-specific BMI cutoffs had been based on less robust measures of diabetes prevalence rather incidence, and had been hampered by small numbers of some ethnic subgroups.
“Our findings should guide revisions of current ethnicity-specific BMI cutoffs to trigger action to reduce the risk of developing type 2 diabetes,” they suggested.
“Such a revision should ensure the provision of appropriate clinical surveillance for patients in minority ethnic populations, commensurate with their greater risk of type 2 diabetes, that would help to prevent the future onset, and therefore facilitate early and effective treatment, of type 2 diabetes,” they concluded.