Amid the rising buzz around Ozempic and similar weight-loss drugs, a group of 58 researchers is challenging the way obesity is defined and diagnosed, arguing that current methods fail to capture the complexity of the condition. They offer a more nuanced approach.

The group’s revised definition, published in The Lancet Diabetes & Endocrinology1 on 14 January, focuses on how excess body fat, a measure called adiposity, affects the body, rather than relying only on body mass index (BMI), which links a person’s weight to their height. They propose two categories: preclinical obesity, when a person has extra body fat but their organs work normally, and clinical obesity, when excess fat harms the body’s organs and tissues.

Conventional methods lead to unnecessary treatment for some people while missing others who need help, he says. To address this, Rubino and his colleagues propose a system for diagnosing obesity that goes beyond BMI, combining it with other methods such as measuring waist circumference, which is a proxy for adiposity, or body scans using low-level X-rays, which can directly measure fat mass.