Imagine three men – one who is 5’ 8”and has a 27-inch waist; the second who is 5’ 6” with a 29-inch waist; and the third male who is 5’ 6” with a 36.6-inch waist. On sight, the first man looks lean, the second is muscular and the third has more fat than the other two. However, all the three men have a body mass index (BMI) of 27 which on paper gives no idea of the difference in their physique.
In 2013, mathematician Dr Diana Thomas gave precisely this example in the journal Obesity arguing that BMI as a measure of adiposity fails to distinguish individuals with similar BMIs but different degrees of fat. Being a mathematician, she proposed a mathematical formula, likening it to pre-calculus eccentricity, that took into account the age, height, weight, sex, race, waist and hip circumference. That result she defined as the Body Roundness Index or BRI.
In June this year, the JAMA Network (a collection of publications from the American Medical Association (AMA) that provides access to medical research, reviews, and perspectives), stated: Obesity, especially visceral obesity, is an established risk factor associated with all-cause mortality. However, the inadequacy of conventional anthropometric measures in assessing fat distribution necessitates a more comprehensive indicator, body roundness index (BRI), to decipher its population-based characteristics and potential association with mortality risk.
This growing recognition of BRI as a valuable tool has led to increased interest among medical professionals. With BRI being the new wonderkid in town, much has been written and discussed about it.
Dr G Moinoddin, consultant bariatric and advanced laparoscopic surgery at Manipal Hospital (Millers Road), Bengaluru, says that although BRI was around since 2013, it is now being considered as the new alternative for the BMI. “Since BRI takes into account the waist and hip measurements, there is a clearer picture of the visceral and subcutaneous fat. The BRI has a score of 1 to 15 and so, more the waist, the higher the BRI. Basically, it gives an idea of the ‘roundness’ of the person.” Or, as Dr Thomas noted in the New York Times, different people can be categorized as different ellipses with their BRI score.
Generally, obesity is scaled by BMI (calculated as weight in kilograms divided by height in metres squared). But experts have noted the association between visceral obesity and mortality; one study published in 2023 by Irfan Khan and Dr Guillaume Paré noted that: The Waist to Hip Ratio or the WHR had the strongest and most consistent association with mortality irrespective of BMI. Clinical recommendations should consider focusing on adiposity distribution compared with mass.
This is where BRI has performed better. It is a more direct measure of adiposity, which strongly correlates with metabolic diseases like type 2 diabetes. In a large retrospective study of 33,000 U.S. adults, researchers found a ‘U-shaped’ association between BRI and all-cause mortality, indicating those with a BRI either below or above the healthy range had an increased risk of death from any cause.
Because measuring body fat is difficult, time-consuming and expensive, the BRI provides a non-invasive way to monitor body composition changes over time, useful for tracking the effectiveness of weight management or lifestyle interventions. It could provide a more accurate measure of central obesity and abdominal fat, which are strongly associated with a higher risk of type 2 diabetes, hypertension, and heart disease, unlike fat accumulated on the buttocks and thighs.
Still, Moinoddin cautions, it is not the magic bullet. “If you really see, be it BMI or BRI, none of them actually consider the body composition, viz, how much fat you have, how much muscle you have, the visceral and subcutaneous fat you have. With a BRI score, it is definitely easier to say if the patient is rounder and wider and if the WHR is unhealthy. A patient with a healthy BRI is slender and considered to be healthier.” However, here’s a catch. A slender and thin person may be considered healthier, but, Moinoddin notes, some thin patients may also have a lot of visceral fat. “This is considered a disadvantage to calculate BRI.”
Other disadvantages of relying on BRI alone are limited clinical validation, as it is still a relatively new measure, which means that its effectiveness and applicability across different populations need further research. Additionally, BRI does not account for muscle mass; individuals with a high muscle-to-fat ratio might receive misleading assessments of their health risks. This can lead to overgeneralization, where individuals who appear healthy according to BRI might still be at risk for metabolic diseases if they have high levels of visceral fat. Therefore, BRI should not be used as a standalone diagnostic tool. Instead, it is most effective when used alongside other measures like lipid profiles, blood sugar levels, and comprehensive metabolic assessments to give a more complete picture of a person’s health.
“The best way to see what is going on inside the body is by checking the lipid profile, blood sugar levels, blood pressure, all the cardiac, renal and liver parameters – all of which play a superior role as compared to BRI,” Moinoddin says.
Still, when you stand in front of the mirror and look at your body and wonder if you are a cylinder, an egg or a barrel, remember the BRI is a better tool (as compared to BMI) to give you a more accurate assessment in a manner that is simple to perform. It seems that the BRI is the new mirror on the wall.
BMI is a simple measurement of body size based on your height and weight. It's limitations are:
BRI is calculated using a formula which takes into account your waist circumference and height. BRI values help estimate body fat distribution, particularly abdominal fat, which is a key indicator of potential health risks. It can be used across different age groups, genders, and ethnicities, making it a versatile tool in global health assessments.
What are its limitations?
While waist circumference measurement is relatively straightforward, it still requires proper technique to ensure accuracy. Inconsistent measurement practices can lead to unreliable BRI scores.
Jayanthi Madhukar is a Bengaluru-based writer.
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