Is the Body Roundness Index the New BMI? What it Says About Your Health

Woman in athletic wear takes a break on a road next to a white and brown dog.
  • The Body Roundness Index is a novel body composition measurement that is touted as being a more accurate alternative to Body Mass Index.

  • In a large retrospective study of 33,000 US adults, researchers found a “U-shaped” curve, indicating those with a BRI below and above the normal range had an increased risk of death from any cause.

  • The study also found that over a 20-year period, BRI showed an upward trend, another indicator of the USA’s obesity epidemic.

Is “body roundness” a good indicator of your weight and health risks? New research says, yes.

Scientists are turning to a novel way to calculate obesity using a system known as the Body Roundness Index, which is touted as a more accurate measurement than Body Mass Index (BMI).

In a new study published in JAMA Network Open, researchers found that a higher BRI was associated with an increased risk of death from any cause in a large retrospective study involving nearly 33,000 US adults.

The research is yet another confirmation of the US’s growing obesity epidemic, but also an indicator of a potential new tool in the fight against obesity. The authors conclude that the BRI is a tool that is almost as easy to perform as BMI, but offers a more accurate assessment of body composition and health risks.

“Our findings provide compelling evidence for the application of BRI as a noninvasive and easy to obtain screening tool for estimation of mortality risk and identification of high-risk individuals, a novel concept that could be incorporated into public health practice pending consistent validation in other independent studies,” the authors wrote.

Body roundness and mortality risk

The study included health data from a large cohort of nearly 33,000 American adults. Researchers pulled the data from the NHANES health database, a self-reported survey that assesses the health and nutrition of Americans.

Researchers looked at a 20-year period of NHANES data between 1999-2018. The average age of cohort members was 46 years old. Half of the group was women. The group was predominantly white (68.26%), but also included Black individuals (10.92%), and Mexican Americans (8.53%).

Then, using BRI which is a slightly more complex body measurement than BMI, they assessed one major outcome: all-cause mortality. The major finding: a “U-shaped” curve of mortality risk associated with BRI score. A U-shaped curve, as its name suggests, shows high risk at either end of a given spectrum, and lower risk in the middle.

In this case, individuals with a BRI below and above the normal range were at greater risk of death from any cause. Meanwhile those in the middle, in the normal range, had the lowest risk. Individuals with a BRI less than 3.4 had a 25% increased mortality risk compared to the normal range, while those with a BRI of 6.9 had 49% increased risk.

Beverly Tchang, MD, an endocrinologist, Spokesperson for the Obesity Society and Assistant Professor of clinical medicine at Weill Cornell Medicine, told Healthline, “It is worthwhile that they are investigating other metrics of adiposity given the known limitations of the body mass index (BMI).

“This is a more direct measure of central adiposity, which strongly correlates with metabolic diseases like type 2 diabetes,” she added.

Researchers also documented a steady increase in average BRI over the 20 year period from 4.8 to 5.62. The trend was more obvious within certain groups, including women, the elderly, and those who identified as Mexican American.

What is the Body Roundness Index?

The Body Roundness Index is similar to the Body Mass Index, but relies on more anthropometric variables.

The BRI which was first proposed in 2013, uses height, weight, waist circumference, and sometimes hip circumference for its calculation. Throw in a dash of theory from 17th century German astronomer Johannes Kepler, and you’ve got the BRI.

Diana M. Thomas, PhD, a Professor of Mathematics at the United States Military Academy at West Point authored the initial paper detailing the concept of BRI explained the concept to Healthline:

“It has to do with geometry. So if you look at Body Mass Index, you can come up with a geometrical explanation.”

Using the necessary variables, you create an image of a circle, but the circle could be more egg-shaped, cylindrical, or maybe totally round. It uses the concept of “eccentricity,” which Johannes Kepler used to quantify planetary orbits. Eccentricity describes how round (like a circle) or narrow (like an ellipse) something is. It represents a number between zero, for a perfect circle, and one.

“With BMI you’re actually using just two measurements. You’re using weight and height. In the Body Roundness Index, we’re using a few more measurements on the human body to capture that shape,” said Thomas.

That BRI number can then be used to make a more accurate calculation of body composition. The closer to zero, the rounder your body, and the greater the risk of all-cause mortality.

How BMI compares

BMI is a simple measurement of body size based on your height and weight that has been used for decades as a general health assessment. Your BMI is a crude measurement of whether or not you fall into a healthy weight range. However, the measurement is far from perfect: it doesn’t distinguish between muscle and fat, for example; so an individual with obesity could very likely have the same BMI as, say, a bodybuilder.

Even with its flaws, BMI is still an important indicator of future health problems. The higher your BMI above normal (anything above 25), and the greater your risk for things like type 2 diabetes, high blood pressure, and cardiovascular disease.

BMI vs BRI

There are plenty of critics of BMI, but there’s no sign that it is going anywhere.

BMI is easy to assess in a doctor’s office or at home. Meanwhile, measuring body fat is more difficult, costly, and time-consuming. It’s not something that can readily be performed during a checkup.

However, BRI could offer a new method of assessing body composition and health risk in a manner that is still simple to perform but offers a more accurate assessment. Forget all that talk about Kepler’s orbiting eccentricities, you don’t need to actually know physics or geometry to perform a BRI test. You just need a few measurements. In fact, you can even plug them into an online calculator if you’re curious about your own BRI.

BRI is still a novel technique that needs further validation, which the study authors note in their paper, so it’s far from commonplace today.

Tchang also notes that the name itself could be a barrier to its future use: “I don’t think BRI is going to catch on simply because “roundness” is a potentially offensive term,” she said.

The bottom line

Researchers used 20 years of American health data to look at mortality risk using the Body Roundness Index.

The BRI is a novel body composition test first proposed in 2013, that some experts believe offers a more accurate alternative to BMI that is similarly easy to perform.

The study found confirmatory evidence of America’s obesity epidemic in gradually increasing BRI over the twenty-year period. The authors also found a “U-shaped” curve indicating greater all-cause mortality risk for individuals with a BRI above and below the normal range.

View the original article on Healthline

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