Forget BMI. This is what we should be measuring
Could ‘body roundness’ be a better gauge of health risk than Body Mass Index (BMI)? Recent studies suggest it might be.
For decades, we’ve relied on Body Mass Index (BMI) to measure healthy weight.
But can a simple weight-to-height ratio really tell the whole story?
New research suggests the Body Roundness Index (BRI) might be a more accurate tool for assessing obesity-related health risks.
So what is it, how do you measure it, and is it time to say bye-bye to the BMI?
Why BMI falls short
The BMI has one big advantage: it’s easy to calculate.
Simply divide your weight by your height squared. Anything below the healthy range of 18.5 – 24.9 is underweight and anything above is overweight.
However, it’s not without its flaws.
“BMI does not provide information about an individual’s body composition – it only calculates the relationship between a person’s height and weight,” says Heart Foundation’s senior manager for healthcare programs and clinical strategy Natalie Raffoul.
“Nor does it assess fat and muscle distribution among other body composition measures.”
That means an athlete with high muscle mass can have an identical BMI to a couch potato, despite very different health profiles.
“It’s not so much what you weigh, but where you carry it, that’s the problem,” says Dr Terri-Lynne South, an obesity management expert at the Royal Australian College of General Practitioners.
“Fat stored around the middle is the biggest indicator of health risks such as cardiovascular disease and diabetes.”
What is the Body Roundness Index?
Developed in 2013, the BRI is a new approach to assessing body composition.
It calculates a score from 1 to 20 based on height, weight, waist, and hip measurements, with 1 indicating a narrow shape and 20 reflecting a rounder body.
A 2024 study analysing the health data of 33,000 American adults over two decades found BRI to be more effective than BMI at predicting overall mortality risk.
Additional research suggests BRI is also better at assessing risks for weight-related diseases including cardiovascular disease, diabetes and cancer.
BRI isn’t perfect (it also doesn’t measure muscle mass), but experts say it provides a more accurate picture.
“Because BRI includes waist and hip measurements, it does give us a better understanding of excessive fat tissue stored around the middle,” Dr South says.
Measuring your BRI at home
You can measure BRI at home, but it involves a complex formula with square roots and ratios.
Fortunately, there’s an online calculator to simplify the process.
However, Dr South says while BRI shows promise, it is still an evolving field.
“BRI is complicated and needs further validation before it becomes widely used,” she says.
Natalie says the accuracy of the results from both BMI and BRI also vary depending on a person’s age, sex and ethnicity.
“BMI and BRI are individual health metrics that assess only one part of an individual’s health and wellbeing,” she says.
“The risk of heart disease is impacted by several factors, including diet, physical activity, family history, blood pressure and cholesterol.
‘That’s why it is important to have a Heart Health Check with your GP from the age of 45 years.”
More on healthy living:
- How to plan and stick to healthy eating on a budget
- The No.1 workout to kickstart your fitness
- Crack of dawn or sunset? The best time to exercise revealed
- 5 diet tips to keep your cholesterol in check
Written by Dimity Barber.
