As the limitations of BMI become more widely recognised, researchers have been developing new body composition metrics that better capture health risk. One of the most talked-about newcomers is the Body Roundness Index (BRI), which uses waist circumference and height to estimate body shape and composition. But is it actually better than the tools we already have?
BRI was developed by Diana Thomas and colleagues at Montclair State University in 2013. It uses an eccentricity-based formula that models the body as an ellipse, using waist circumference and height to estimate how "round" a person's body is. The result is a number typically between 1 and 20, where higher values indicate rounder body shapes and greater central adiposity.
The formula involves some complex mathematics — pi, square roots, and eccentricity calculations — which makes it harder to compute mentally than WHtR's simple division. However, the underlying inputs are the same: waist circumference and height.
Because BRI uses the same two measurements as WHtR (waist and height), the two metrics are mathematically related. In fact, some researchers have pointed out that BRI is essentially a more complex transformation of the waist-to-height ratio. Studies comparing the two have generally found similar predictive power for cardiovascular disease and metabolic syndrome.
Both BRI and WHtR outperform BMI for predicting cardiometabolic risk, and for the same fundamental reason: they incorporate waist circumference, which captures abdominal fat distribution that BMI completely ignores.
BRI proponents argue that its eccentricity model provides a more nuanced picture of body shape than a simple ratio. The formula was designed to correlate more closely with DEXA-measured body fat percentage, and some validation studies have shown marginally better correlation with body fat than WHtR in certain populations.
BRI also gained significant public attention after a 2024 study in JAMA Network Open linked higher BRI values to increased all-cause mortality, bringing the metric into mainstream health conversations.
The primary criticism of BRI is that it adds mathematical complexity without clear clinical benefit over WHtR. Since both metrics use the same inputs, their predictive power is similar. WHtR has the advantage of a simple, universally understood threshold (0.5), while BRI requires reference tables to interpret.
BRI also lacks the decades of validation across diverse populations that WHtR has accumulated. Clinical guidelines and public health campaigns have not yet adopted BRI thresholds, making it harder for individuals and clinicians to act on the results.
For most people, WHtR provides the same information with far less complexity. The simple rule of keeping your waist under half your height is easy to remember, easy to calculate, and well-supported by evidence. If you are already measuring your waist and height, you are essentially capturing the same data that BRI uses.
BRI may become more clinically useful as research matures and standardised thresholds are established. For now, it is worth being aware of as an emerging metric, but WHtR remains the more practical choice for self-screening.
Whether you use BMI, WHtR, BRI, or all three, the most important message is the same: abdominal fat matters, and simple measurements can flag elevated risk. No single number captures the full picture of health. Use these tools as conversation starters with your healthcare provider, not as final verdicts.