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A growing crisis in obesity levels demands that diagnosis be radically overhauled to improve help for patients who have already been made ill by the condition, according to an international commission backed by leading medical bodies.
Reclassifying obesity into “pre-clinical” and “clinical” types should improve access to treatment for millions of people most at risk of serious conditions such as irreversible organ damage, the review says.
The more than doubling of global obesity rates in 30 years has triggered an urgent search for better diagnostic tools than the numerical body mass index, which offers little insight into the health damage caused by the condition.
The sharp rise in obesity has piled costs on health systems and driven huge demand for weight-loss drugs such as Ozempic, Wegovy and Mounjaro. The booming market is projected to reach at least $80bn in sales by 2030.
But many obesity patients do not receive treatment, such as surgery to make the stomach smaller, because they do not fit existing BMI-based criteria, said Professor Francesco Rubino, who led the work by the Lancet diabetes and endocrinology commission.
“The definition we have of obesity doesn’t fit with the spectrum that it represents,” said Rubino, a metabolic and bariatric surgery specialist at King’s College London. “I’ve seen a lot of people who not only struggle with objective illness, sometimes very severe, but very often don’t get access to treatment.
“We lack a fundamental, crucial missing piece — which is a clinical diagnosis and an illness definition.”
BMI — a calculation based on height and weight — can both underestimate and overestimate body fat, the commission said in a paper published in The Lancet on Tuesday. A very muscular person may be obese by the BMI definition because they are heavy, for example.
The commission, which included 58 medical experts, focuses instead on identifying those suffering observable obesity-related health problems rather than simply a risk of them. It defines clinical obesity as a “chronic, systemic illness characterised by alterations in the function of tissues, organs, the entire individual or a combination thereof”, because of excess body fat.
The commission recommends initially assessing obesity status using additional indicative measures such as waist-to-height ratios, or technological tools that measure fat concentration such as X-rays and responses to electric current. Clinical obesity would then be diagnosed based on a list of criteria including measures of breathing, heart and liver functions.
The work has been endorsed by 76 organisations, including scientific societies and patient advocacy groups, that span the Americas, Europe, Asia, the Middle East and Africa.
A redefinition of obesity would have potential implications for the use of weight-loss drugs. These are expensive for national health systems to prescribe widely, meaning that some may offer them based on perceived degree of need.
Other scientists welcomed the commission’s work, although some pointed to potential limitations such as the additional financial burden on healthcare systems. These include the cost of advanced diagnostic methods such as X-ray scans.
The call for new diagnostic criteria might be complicated for doctors to apply and also underemphasise the impact of obesity on patients’ mental health, said Alexandra Cremona, associate professor of human nutrition and dietetics at the University of Limerick. But these problems are “not insurmountable”, she added.
The commission’s proposals might also be difficult to implement because codes used to classify diseases for surveillance purposes and payment systems were “entrenched” and hard to modify, said Donna Ryan, professor emerita at the Pennington Biomedical Research Center in the US.
“My concern is that the report raises awareness, promotes discussion, but doesn’t make the next step to give us any practical solutions,” said Ryan, who stressed she was “trying to be optimistic” about the work. “Maybe that can be the next project.”
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