Body roundness index (BRI) is being touted as a possible alternative to BMI, but experts are divided on how useful the tool may be in a clinical setting.

“It is likely that in certain sub-populations, BRI may be a more sensitive tool to predict the risk of health conditions that are directly linked to visceral obesity,” said Yulia Zak, MD, a clinical assistant professor of surgery at Stanford, in speaking with MDLinx. “However, studies to date have failed to unequivocally demonstrate BRI’s superiority over BMI in predicting cardio-metabolic risk in diverse populations.”

Even so, a 2024 study of more than 30,000 people found that associations between BRI and all-cause mortality displayed a U shape, meaning that those in the lowest and highest BRI groups had a significantly increased risk of all-cause mortality.

Zhang X, Ma N, Lin Q, et al. Body roundness index and all-cause mortality among US adults. JAMA Netw Open. 2024;7(6):e2415051.

The study authors argue that, pending confirmation from other studies, BRI could represent a novel approach to be used in public health practice.

BRI explainer

Unlike BMI, which only takes into account weight and height, BRI factors in waist circumference. This means that, as a measure, the BRI can highlight visceral fat distribution. Research has found that BRI is more effective in estimating risk for cardiometabolic disease, kidney disease, and cancer than other anthropometric measures.

Zhang X, Ma N, Lin Q, et al. Body roundness index and all-cause mortality among US adults. JAMA Netw Open. 2024;7(6):e2415051.

But like BMI, BRI is far from a comprehensive measurement of health. For example, it doesn’t account for sex-based differences.

“Men tend to carry more fat in their trunk or in their abdominal area, whereas women tend to deposit more on their lower body in the hips,” explains Mir Ali, MD, a board-certified bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, CA.

“I see patients who have really large lower bodies and a relatively normal-shaped trunk, and this would not take that into account. So it's not a perfect measure by any means, and I don't think we've found a perfect measure yet,”“The perfect measure would be something that's non-invasive, easy to implement, easy to calculate, and gives a good estimate of somebody's health,” Dr. Ali continues. “There's a lot of different factors that contribute to somebody's health, so I don't know that we'll ever find a perfect measure, but all of these indices, like body mass index and body roundness index, are good tools.”

The best tool in the clinical setting

While research suggests BRI may prove more accurate than BMI in certain areas, experts remain unsure whether it warrants replacing BMI in a clinical setting. John Thyfault, PhD, professor in the Department of Cell Biology and Physiology and in the division of Endocrinology, Metabolism and Genetics at the University of Kansas Medical Center, shared some of the limitations with MDLinx.

“Including the waist (and hip if possible) along with height and weight is more accurate for cardiometabolic risk. But we have known this for a long time and nothing has changed. Until there is some sort of device that a patient steps into that measures these things automatically, I think most clinics are not going to want to take the time to do this, nor trust that staff shuttling patients through vitals quickly are going to do it accurately. It is easy to get off-target measures and thus not have consistent measures over time.”

Flaws of BMI

“What is common to all indirect measures is that they are essentially estimation equations that fit large populations well and individuals poorly,” said Joseph E. Donnelly, Jr., EdD, professor in the Division of Physical Activity and Weight Management at the University of Kansas Medical Center.

“Unfortunately, there are no easy/cheap ways to get actual body composition, thus folks tend to fall back on estimation equations frequently with inaccurate results. Will the 'roundness' equations solve this? Highly doubtful.”