Global report urges more accurate definition of obesity than body mass index

Too many people are at risk of being diagnosed with obesity when a “more precise” and “nuanced” definition is needed, Reports from global experts explain.

Doctors should consider the overall health of patients with excess fat, rather than just measuring their body mass index (BMI), the report said.

Those who have chronic health conditions related to their weight should be diagnosed as “clinically obese,” while those with no health problems should be diagnosed as “preclinical obesity.”

It is estimated that more than one billion people worldwide suffer from obesity, and prescription weight-loss drugs are in high demand.

The report was published in The Lancet Diabetes & Endocrinology and was supported by more than 50 medical experts around the world.

“Obesity is a spectrum,” said Professor Francesco Rubino of King's College London, chair of the group.

“There are people who have this disease and manage to live normal lives and function normally.

“Others cannot walk or breathe well, or have serious health problems and are wheelchair-bound.”

The report calls for a “redefinition” of obesity to distinguish between patients who have the disease and those who remain healthy but are at risk of developing the disease in the future.

Currently, in many countries, obesity is defined as BMI over 30 – A measurement method for estimating body fat based on height and weight.

Weight loss drugs such as Wegovy and Mounjaro are usually restricted to such patients.

In many parts of the UK, the NHS also requires people to have a weight-related health condition.

But the report says body mass index cannot reveal a patient's overall health, nor can it differentiate between muscle and body fat, or account for more dangerous fat around the waist and organs.

Experts advocate a new model to study the signs of obesity that affect the body's organs – such as heart disease, breathing difficulties, type 2 diabetes or joint pain – and their damaging effects on daily life.

This suggests that obesity has become a clinical disease requiring pharmacological treatment.

However, those with “preclinical obesity” should receive weight loss advice, counseling and monitoring rather than drugs and surgery to reduce the chance of developing health problems. Treatment may also be necessary.

Professor Rubino said: “Obesity is a health risk – the difference is that for some people it is also a disease.”

He added that it would be wise to redefine it to understand risk levels in large groups of people, rather than the current “fuzzy picture of obesity”.

Waist-to-height ratio or direct fat measurement and a detailed medical history can provide clearer information than BMI, the report said.

Professor Louise Ball, an expert on childhood obesity at the University of Sydney who contributed to the report, said the new approach would allow adults and children with obesity to receive “more appropriate care” while reducing overdiagnosis and unnecessary treatment number of people.

The report said this “redefinition” of obesity “makes more sense” at a time of widespread use of drugs that can reduce body weight by up to 20 percent because it “improves diagnostic accuracy.”

The Royal College of Physicians said the report lays a solid foundation for “treating obesity with the same medical rigor and compassion as other chronic conditions”.

The academy said distinguishing between preclinical and clinical obesity would be “an important step forward” and “underscores the need for early identification and intervention” while delivering the right care to patients whose health is already severely affected.

But there are concerns that pressure on health budgets could mean less income for “pre-obese” people.

Professor Jim Mann, co-director of the Edgar Diabetes and Obesity Research Center in Otago, New Zealand, said the focus was likely to be on “the needs of those defined as clinically obese” and that limited funding was “very limited”. Likely” was directed at them.