Expert commission proposes adding waist measurement to BMI in defining obesity

On 14 January 2025, an international commission of experts published a proposal in The Lancet Diabetes & Endocrinology to change how obesity is defined. Body mass index (BMI), the ratio of weight to height squared, had long been the main yardstick, but the group argued it says little about where fat is stored or whether it harms health.

The commission recommended combining BMI with at least one other measure of body fat, such as waist circumference, waist-to-hip ratio or waist-to-height ratio. People with a high BMI but normal fat measures might not count as having excess fat, while others with a normal BMI and a large waist could be identified.

The report also proposed two categories. Clinical obesity would describe excess fat that already impairs organ function or daily life, while preclinical obesity would describe excess fat without such effects but with a higher future risk. The authors said this could help doctors prioritise treatment. Many medical societies endorsed the proposal, while others raised concerns about how many more people would be classed as obese.