Body roundness index

Body roundness index
BRI vs height (vertical axis) vs waist circumference (horizontal axis)

Body roundness index (BRI) is a calculated geometric index used to quantify an aspect of a person's individual body shape. Based on the principle of body eccentricity, it provides a rapid visual and anthropometric tool for health evaluation.^[1]

Introduced in 2013, the BRI calculation can be used to estimate total and visceral body fat. Ranges of healthy body roundness have been established to accurately classify people with healthy fat mass (weight) compared to obese people who are at risk for morbidities.^[1]

Compared to traditional metrics, such as the body mass index (BMI), (which uses weight and height), BRI may improve predictions of the amount of body fat and the volume of visceral adipose tissue. Despite its common use, BMI can misclassify individuals as obese because it does not distinguish between a person's lean body mass and fat mass. Instead, BRI quantifies body girth as well as height, potentially providing more accurate estimates of fat mass.

BRI scores range from 1 to 16, with most people between 1 and 10, although people with scores of 6.9 and up – indicating wider, rounder bodies – were found to have a risk of all-cause mortality that was increased by up to 49% compared to people having a medium BRI of 5.^[2][3] In a 2020 review, high BRI was associated with increased risk of metabolic syndrome and several other diseases.^[4]

Typical American adult BRI values range from 3 or less (midsection leanness) to 7 or more (midsection roundness), with a medium index of about 5.^[1][3] As a relatively newer predictive metric, BRI has a smaller research record compared to established indices like the BMI, waist-to-hip ratio indicating its accuracy and uses remain to be fully established in clinical research. Conversely, the simple waist-to-height ratio (which uses the same measurements) has a better research base, leading to its adoption as the preferred guideline in some countries.