BMI, or body mass index, has long been used as a simple calculation to determine if someone is underweight, a ‘healthy’ weight or obese.But when it was devised by a Belgian mathematician almost 200 years ago, it was never supposed to be a tool to measure health.Now, researchers are challenging the way obesity is defined and diagnosed. Today, a look at the new approach and why there’s a global push away from BMI.First published 10 February, 2025Featured: Willow Moscarda, Perth studentDr Louise Bauer, Professor of child and adolescent health, University of Sydney