Study: BMI Measurements Should Be Tailored To Race and Ethnicity

A new study suggests that body mass index (BMI) measurements widely used to assess health risks such as obesity and diabetes are not an accurate method for non-White people. 

Researchers examined data from over 1.4 million people in England between 1990 and 2018 and, through statistical analysis, distinguished patterns according to the participants’ race and ethnicity. 

They found that the current standard BMI cutoffs used to assess some threats to health should be much lower for non-White populations.

These findings suggest that a “one-size-fits-all” cutoff doesn’t actually work for everybody. Researchers are hopeful these findings will encourage revision of BMI cutoffs based on more precise data, and help better cater to the needs of different populations.

“I don't think we should be creating policy which is based on data where the affected population is not included,” lead study author Rishi Caleyachetty, PhD, an epidemiologist at the University of Warwick, U.K., tells Verywell. He mentions that, for example, some non-White populations are more heavily hit by type 2 diabetes and obesity than White populations. “Here we are implementing policy based on data.”

The study was published last week in The Lancet Diabetes & Endocrinology journal.

BMI Cutoffs Aren't Accurate For All

BMI is a measurement that looks at a person’s weight in kilograms divided by the square of their height in meters. Where somebody lies on the BMI spectrum can indicate varying levels of body fat. It's typically used to screen for your risk of developing different health issues.

The researchers closely examined a dataset recording BMI and type 2 diabetes for 1,472,819 people. They included White, South Asian, Black, Chinese, and Arab people in their data. Typically, people with a BMI of 30 and above are thought to be more at risk of developing type 2 diabetes.

They found, however, that the BMI cutoffs for type 2 diabetes were actually:

• 23.9 for South Asian people
• 26.9 for Chinese people
• 28.1 for Black people
• 26.6 for Arab people

“The key thing here is that people from these ethnic minority communities will have assumed that they are okay in terms of their weight status, and possibly not gone to seek advice, because their primary care provider has not thought that they're in the range for it, because we have cutoffs,” Caleyachetty says.

Adjustments Are Needed

Tailoring these cutoffs by ethnicity might help improve early intervention by giving patients the attention they need before the problem gets serious.

“This is a great retrospective review of clinical data,” Jerry Bailey, clinical director at Lakeside Holistic Health, who was not involved with the study, tells Verywell. “While this is a first step to just look at BMI as an indicator of disease occurrence, it opens the door to really start speaking about the lack of diversity in health-related measures.”

“As the research noted this will allow better overall post-diagnosis management of lifestyle diseases,” Bailey adds. “It also allows us to initiate preventative care earlier versus watching and waiting until the disease shows up. The ‘ounce of prevention equals a pound of cure’ really is demonstrated here.”

Although a World Health Organization expert consultation recommended that a BMI of 27.5 or above for South Asians and Chinese should trigger action to prevent type two diabetes, that’s still too approximate according to Caleyachetty. 

“That value was based on a small number of studies which didn't even include South Asian people from an Indian, Pakistani, Bangladeshi background. It didn't include Black African, Black Caribbean, Arabs as well,” Caleyachetty says. “So it was based on very limited evidence.” 

It’s still unclear exactly why the correlation between BMI and type 2 diabetes is different between different population slices, but it’s probably a combination of:

• Genetics
• Biochemical characteristics
• Body composition
• The way different bodies store fat differently
• Lifestyle

More research is needed to better understand this, Caleyachetty says.

In general, researchers from different areas of study are working towards perfecting the concept of BMI overall. “There's a lot of debate about BMI, whether it's a good measure or a bad measure. It is an imperfect measure,” Caleyachetty says. “And in time I suspect that it may be improved upon.”