Black and Asian adults may be at risk for developing diabetes at a lower weight than whites, according to a new study.
Based on the findings, researchers suggest the definition of obesity should be different for different populations, in order to trigger diabetes interventions in a timely manner.
Overweight defined using BMI
Body mass index (BMI) is a measure of weight in relation to height used to assess health risks. The Centres for Disease Control and Prevention (CDC) defines overweight as a BMI of 25 to 29.9 and obesity as a BMI of 30 and above.
Read: High BMI bad for brain
However, those cutoffs are primarily applicable to white people, which has been noted by the World Health Organization (WHO), Dr. Naveed Sattar told Reuters Health.
"But few people really recognize this," he said. Institutions like the WHO and CDC have yet to adopt ethnicity-specific BMI cutoffs for overweight and obesity.
Sattar worked on the study at the Institute of Cardiovascular and Medical Sciences at the University of Glasgow in the UK.
He and his team analyzed data on almost 500,000 middle-aged UK adults, 96 percent of whom were white. The remaining four percent included South Asian, black and Chinese adults.
Five percent of the total group, or about 25,000 people, had diabetes, according to findings published in Diabetes Care.
Compared to whites, nonwhite adults were at least twice as likely to have diabetes. Diabetes rates for white people with a BMI of 30, the lower threshold for obesity, were equal to diabetes rates for South Asians with a BMI of 22, black people with a BMI of 24, Chinese women with a BMI of 24 and Chinese men with a BMI of 26.
Results were similar when the researchers looked at waist circumference: non-white people were at risk for diabetes at smaller waist sizes than white people.
Read: Risk for diabetes
Recommendation from NICE
In 2013, the National Institute for Health and Care Excellence (NICE) in the UK recommended new BMI thresholds for intervening to prevent ill health among ethnic minorities including people of African, Caribbean and Asian descent. The group indicated an increased risk of chronic conditions at a BMI of 23 or higher and a high risk of chronic conditions starting at a BMI of 27 for those people.
"The guidance and briefing documents make recommendations for health services and local government to take action," Dr. Tonya Gillis, media relations manager for NICE, told Reuters Health by email. She noted that NICE public health guidance only applies to England and not to international standards.
Researchers have suggested that a combination of genetic and environmental factors play a role in different body fat patterns by ethnicity, but questions remain.
Read: Environment and weight
Obesity cutoff for Asians
The new study and others suggest that the obesity cutoff for Asians in particular might need to be reevaluated, Sattar said.
The report included many people but only addressed one point in time, he noted. These findings need to be verified by another study that follows a group of people over time, he said.
Establishing ethnicity-specific cutoffs for obesity is important partly to make doctors aware that diabetes risk can be heightened at much lower BMIs for some ethnicities, which should prompt them to give lifestyle advice and screen for diabetes at lower weights, Sattar said.
"If any population of people are at an increased risk of developing a range of serious conditions, then it's vital to highlight any relevant risk factors that can help professionals and the individuals affected to take action at the earliest opportunity," Gillis said.
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