The World Health Organisation's cut-off point for obesity should be revised in South Asian people to take into account new evidence that they are at high risk of diabetes at even lower BMIs than had been appreciated, researchers conclude.
The WHO already recommends lower cut-off points for classification of overweight and obesity in Asian populations – 23 kg/m2 and 27.5 kg/m2, compared with the conventionally used 25 and 30 – but the authors of a new study suggest this correction does not go far enough.
Their research looked at 1,353 South Asians and 4,688 White Europeans registered at GP practices in Leicester between 2004 and 2007. Participants were randomly selected and invited for glucose and cardiovascular risk assessment – those with known diabetes were excluded.
Researchers used linear regression to assess the relationship between BMI and waist circumference, and risk factors including blood lipid levels, fasting glucose, 2-hour glucose, HbA1c and blood pressure.
South Asian men have the same levels of dysglycemia at a BMI of 22 as White European men had with a BMI of 30. In women, a BMI of 21.5 for South Asians was equivalent to 30 for White Europeans. Waist circumference cut-off points were also significantly lower for South Asians – 83.8 cm in men and 69.3cm in women, compared with 102cm and 88cm for White European men and women respectively.
Study leader Professor Kamlesh Khunti, professor of primary care diabetes at the University of Leicester and a GP in the city, said the majority of the South Asian population in developed countries had a BMI higher than the cut-off points suggested in this study.
‘The vast majority of South Asians will have a higher risk of cardiometabolic disease, particularly type 2 diabetes, than a White European with a BMI of 30. Consequently South Asian ethnicity per se should be viewed as denoting a similar level of risk as obesity does in White Europeans.'
Dr Colin Kenny, a GP in Dromore, County Down, said: ‘GPs should be aware of these considerable differences in varied populations when assessing overall cardiovascular risk.'
Dr Kambiz Boomla, a GP in Tower Hamlets, East London said the study had implications for GPs in targeting lifestyle advice to thinner South Asian people – ‘to offer like-for-like programmes to people at the same risk'.
Consultant in diabetes and metabolic medicine at The Royal London Hospital, Dr Tahseen Chowdhury, said:
‘The epidemic of diabetes is being felt intensely in South Asian migrant populations and in the Asian subcontinent itself. Prevention measures will have to focus on stopping weight gain, increasing physical activity and overcoming cultural barriers to addressing these issues.'
‘I can't help thinking that a ‘nudge' will just not be enough.'
PLoS ONE, October 19 2011