BMI may not accurately measure health in black people, major study finds
- Body mass index may not be an accurate measure of health for everyone, a new study suggests.
- Data from 1.5 million people found public health advice was based on risk levels for white people.
- Current medical standards may lead to health inequities for black and Asian people, researchers said.
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Evidence suggests body mass index (BMI) may not be a helpful measuring tool for black people.
BMI is often used to assess risk of diabetes and other chronic conditions, but it could cause dangerous health inequities for black and South Asian people, and other populations, according to research published earlier this month in The Lancet Diabetes and Endocrinology and presented at the 2021 European Congress on Obesity.
Researchers from several universities, including Oxford, looked at data from more than 1.5 million adults in the UK who initially did not have diabetes to find patterns between BMI and the risk of developing type 2 diabetes.
They found that the point where higher BMI was linked to higher diabetes risk was different between populations. For white people, a BMI of 30 or above was linked to more risk. For black participants, the cut-off point was a BMI of 28 or above, and for South Asian people it was significantly lower, at a BMI of 23.9 or above.
"This study shows that the one size fits all approach really does not work for BMI and type 2 diabetes risk when we look at the UK's diverse population," Dr Rishi Caleyachetty, lead author of the study and an epidemiologist at the University of Warwick, said in a press release.
These findings are significant because many public health organisations currently recommend treatments or lifestyle changes for people based on their BMI. But those numbers are only consistent with risk levels for white people, the study suggests. If, as the data shows, black and Asian populations have a different threshold of risk, they may not be getting the care they need in time, the researchers noted.
"As a doctor, I'm extremely concerned that if the current BMI values used for black, Asian and minority ethnic people are not appropriately amended, many will needlessly slip through the net, leaving them unknowingly at risk of type 2 diabetes," Caleyachetty said in the press release.
It's not clear from the current research why diabetes risk may be greater at a lower BMI for certain populations - the researchers note in the study that factors like genetics, body composition, and lifestyle may all play a role.
BMI has been critiqued for its limitations, including racial disparities
This isn't the first time that experts have questioned the use of BMI in assessing health risks. The measurement refers to the ratio between a person's height and weight. As a metric for disease risk, it doesn't account for other factors (like body composition) that are crucial for assessing a person's unique health needs.
"On an individual level, BMI may not be a perfect indicator of someone's health risk. It's one of several measurements that we have to assess health risks," Dr W Scott Butsch, director of obesity medicine at the Cleveland Clinic, previously told Insider.
Given the metric's roots, it's no surprise that BMI may be unhelpful for black people. The measurement was first created in the 19th century and was based on what was typical for white Europeans at that time, and critics have pointed out that BMI relies on outdated and narrow definitions of a "normal" weight.
Previous research has also found racial disparities in how accurately BMI indicates health. A 2020 study from Stanford found that for black women, the threshold of risks for chronic illnesses is a BMI of 31-33, and many people could be considered healthy at a higher BMI. In contrast, for white and Hispanic women, the cutoff for disease risk was lower, a BMI between 25-29.
Findings like these suggest more research is needed to update current health recommendations so they can better serve a diverse population, the researchers concluded.
"This work highlights that we need evidence for all ethnic groups as they are at risk of diabetes at different levels of BMI. A blanket approach is not acceptable any longer," Dr Paramjit Gill, professor at the University of Warwick and co-author of the study, said in the press release.
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