What is body roundness index (BRI)? Can it be an alternative to BMI?

How do you measure a person’s health? Body Mass Index (BMI) is the answer we all know. But BMI could soon be passé. A new metric has caught the attention of health experts and enthusiasts alike. It’s called the Body Roundness Index (BRI).

BMI has long been the go-to tool for assessing health based on height and weight. However, scientists are now exploring BRI as a new, more accurate way to measure obesity. But what is it?

What is the body roundness index (BRI)?

The Body Roundness Index (BRI) considers an individual’s height and waist circumference to assess their health status. It measures how round or circular a person’s body shape is by using a formula that considers height and waist circumference, but not weight.

The BRI, say experts, offers a more accurate assessment of central obesity and abdominal fat, both of which are strongly associated with an elevated risk of developing Type 2 diabetes, hypertension, and heart disease, in comparison to fat stored in the buttocks and thighs, The New York Times reported.

Several online calculators allow you to input your height, waist, and hip measurements to calculate your BRI. After entering your data, you will receive a score that indicates whether you fall within the “healthy zone” or not.

Who developed BRI?

BRI was developed by mathematician Diana Thomas, now a professor at the United States Military Academy in West Point, New York. She first introduced this index in a 2013 article in the journal Obesity.

Speaking to The Hindu, Thomas said, “The more round you are, the higher per cent body fat you have, the higher your visceral adipose and therefore your risk of diabetes, cardiovascular problems etc. Metabolic illnesses can manifest without the body looking like it is obese. But even at the lower end, having a small body size for height, weight and gender, is a risk. The green zone shows you the sweet spot.”

What’s the problem with BMI?

The Body Mass Index, or
BMI, is a simple height-to-weight ratio which has been a regular in medical examinations for years. While it is still one of the most commonly used health measures, it is also criticised for categorising people as overweight, obese, or severely obese. It also does not tell the difference between fat and muscle.

A BMI of lower than 18.5 is classified as underweight, between 18.5 and 25 as normal weight, from 25 to 30 as overweight, and anything above 30 is considered obese. The metric has been questioned by athletes and bodybuilders.

With a BMI of 30, American rugby player then falls in the “overweight category”. So would actor Arnold Schwarzenegger when he was a bodybuilder, reports NYT.

Last year, the American Medical Association issued a policy statement which declared that BMI fails to consider factors such as race, sex, age, ethnicity, and gender diversity. “It doesn’t take body composition into consideration,” Maya Feller, a registered dietitian and nutritionist, told ABC News. “So someone who’s very muscular might wrongly be put in the overweight or
obese category, and that’s just not okay.”

BRI vs BMI: Which is more accurate?

Unlike the BMI, which considers only height and weight, the BRI includes both height and waist circumference, providing a more precise evaluation of body fat distribution and associated health risks, according to the National Institutes of Health, US.

Notably, a huge advantage of BRI is its focus on abdominal fat, which is closely tied to metabolic disorders and cardiovascular issues. Meanwhile, BMI only assesses overall body weight without addressing fat distribution.

BRI calculates a value that typically ranges from 1 to 20, with extreme scores indicating heightened health risks. This index then categorises individuals as healthy or unhealthy by the inclusion of abdominal fat, something that BMI fails to achieve.

While more methods like dual-energy X-ray absorptiometry (DXA) and magnetic resonance imaging (MRI) can accurately measure body fat levels, these approaches require considerable resources.

How reliable is BRI?

Several studies have now shown that the BRI may be more effective at predicting health risks compared to BMI.

A recent study involving over 32,000 US adults, titled ‘Body Roundness Index and All-Cause Mortality Among US Adults’, published in JAMA Network Open, revealed a U-shaped association between BRI and all-cause mortality. This suggests that both the lowest and highest BRI groups face an increased risk of mortality, indicating that “BRI may be promising as a newer anthropometric measure associated with all-cause mortality.”

However, it may be subject to human error as well. In an article for The Conversation last year, Alice Bullas, a senior research fellow at the Sports Engineering Research Group at Sheffield Hallam University, said that a study found eight out of 10 trained health professionals showed such high levels of measurement error when manually assessing abdominal size that they failed to detect a three cm increase on a measurement later.

She also pointed out that, as a relatively new metric, the BRI lacks extensive data supporting its use that is available for BMI.

Will BRI replace BMI?

While recent research suggests that the BRI might be a better overall health indicator, it is unlikely to replace standard BMI measurements for now, according to Healthline.

Whether at home or in a hospital, BMI is easy to access. In comparison, measuring body fat can be more challenging, expensive, and time-consuming, making it unsuitable for quick assessments during checkups.

As a relatively unexplored approach, BRI requires more validation since it is not yet widely adopted in practice.

What are some other ways to assess health?

Maya Feller, speaking to ABC News, said that although both BRI and BMI can be valuable tools, tests that assess a person’s internal health should be prioritised instead of focusing on weight or measurements.

“I always like to check the insides,” she said. “You can look as wonderful as you want on the outside, but what’s happening with your lipids? What’s happening with your blood pressure, your blood sugars? Those are the things that I want to see.”