Beyond BMI: global commission proposes new way to diagnose obesity

Doctors worldwide should diagnose obesity differently, relying on broader criteria and taking into account when the condition causes ill-health, according to a new framework drawn up by experts and endorsed by 76 medical organizations internationally.

At the moment, clinicians use BMI or body mass index to diagnose obesity, a calculation based on a person’s weight and height. But this tool is not precise enough and they should also take other measurements, such as waist circumference, to avoid misdiagnosis, the 56 experts who took part in the global commission said.

Obesity should also be split into two categories, ‘clinical obesity’ and ‘pre-clinical obesity’, the commission said, in a paper published on Tuesday in The Lancet Diabetes and Endocrinology journal.

Clinical obesity involves excess body fat plus symptoms of reduced organ function – like breathlessness or heart failure – or problems going about daily life. It should be considered as a chronic disease and treated accordingly, the experts propose.

Pre-clinical obesity is obesity or excess body fat without any signs of ongoing illness, and normal organ function. It should be considered a risk factor both for clinical obesity and other illnesses like diabetes, the commission said, and patients should be supported to reduce that risk, either through monitoring or active treatment.

“Obesity is a spectrum,” said commission chair, Francesco Rubino, a professor at King’s College London, at a press conference earlier this week.

More than one billion people are currently estimated to have obesity globally.

The experts said they aimed to make diagnosis more precise, which could help better use healthcare resources. They said it was not yet clear if it would lead to more or fewer people being diagnosed, but they hoped it would settle the polarising debate within the medical establishment over whether obesity is a disease.

“We cannot afford to have a blurry picture of obesity,” said Rubino.

The guidelines were backed by organisations including the American Heart Association and the Chinese Diabetes Society, as well as the World Obesity Federation.

World Health Organization experts served on the commission, which began work in 2019.

The advent of the GLP-1 class of drugs to treat obesity, first developed by Eli Lilly and Novo Nordisk, had changed the landscape since then, Rubino said, but the use of the drugs was not the commission’s focus. However, he said clearer diagnosis, if adopted by healthcare systems worldwide, could help doctors decide when best to prescribe them based on individual risk.

The commission also said it could mean health insurers may consider covering the drugs for clinical obesity as a standalone illness. Many currently require another related condition to be present, like diabetes.

“We hope this leads to a change in practice, and maybe even before that, a change in mindset,” said Rubino.