A New Disease Definition, ‘Clinical Obesity’

SAN ANTONIO, Texas — An upcoming document will entirely reframe obesity as a “condition of excess adiposity” that constitutes a disease called “clinical obesity” when related tissue and organ abnormalities are present.

The authors of the new framework are a Lancet Commission of 56 of the world’s leading obesity experts, including academic clinicians, scientists, public health experts, patient representatives, and officers from the World Health Organization. Following peer review, it will be launched via livestream and published in Lancet Diabetes & Endocrinology in mid-January 2025, with formal endorsement from more than 75 medical societies and other relevant stakeholder organizations.

On November 4, 2024 at the Obesity Society’s Obesity Week meeting, the publication’s lead author, Francesco Rubino, MD, Chair of Bariatric and Metabolic Surgery at King’s College London, London, United Kingdom, gave a preview. He began by noting that despite the declaration of obesity as a chronic disease over a decade ago, the concept is still debated and not widely accepted by the public or even by all in the medical community.

“The idea of obesity as a disease remains highly controversial,” Rubino noted, adding that the current body mass index (BMI)-based definition contributes to this because it doesn’t distinguish between people whose excess adiposity place them at excess risk for disease but they’re currently healthy vs those who already have undergone bodily harm from that adiposity.

“Having a framework that distinguishes at an individual level when you are in a condition of risk and when you have a condition of disease is fundamentally important. You don’t want to blur the picture in either direction, because obviously the consequence would be quite significant… So, the commission focused exactly on that point,” he said.

The new paper will propose a two-part clinical approach: First, assess whether the patient has excess adiposity, with methods that will be outlined. Next, assess on an organ-by-organ basis for the presence of abnormalities related to excess adiposity, or “clinical obesity.” The document will also provide those specific criteria, Rubino said, noting that those details are under embargo until January.

However, he did say that “We are going to propose a pragmatic approach to say that BMI alone is not enough in the clinic. It’s okay as a screening tool, but when somebody potentially has obesity, then you have to add additional measures of adiposity that makes sure you decrease the level of risk… Once you have obesity, then you need to establish if it’s clinical or nonclinical.”

Asked to comment, session moderator John D. Clark, MD, PhD, Chief Population Health Officer at Sharp Rees-Stealy Medical Group, San Diego, California, told Medscape Medical News, “I think it’ll help explain and move medicine as a whole in a direction to a greater understanding of obesity actually being a disease, how to define it, and how to identify it. And will, I think, lead to a greater understanding of the underlying disease.”

And, Clark said, it should also help target individuals with preventive vs therapeutic approaches. “I would describe it as matching the right tool to the right patient. If a person has clinical obesity, they likely can and would benefit from either different or additional tools, as opposed to otherwise healthy obesity.”

Rubino told Medscape Medical News he hopes the new framework will prompt improvements in reimbursement and public policy. “Policymakers scratch their heads when they have limited resources and you need to prioritize things. Having an obesity definition that is blurry doesn’t allow you to have a fair, human, and meaningful prioritization… Now that we have drugs that cannot be given to 100% of people, how do you decide who gets them first?” I hope this will make it easier for people to access treatment. At the moment, it is not only difficult, but it’s also unfair. It’s random. Somebody gets access, while somebody else who is very, very sick has no access. I don’t think that’s what we want.”

Miriam E. Tucker is a freelance journalist based in the Washington DC area. She is a regular contributor to Medscape Medical News, with other work appearing in the Washington Post, NPR’s Shots blog, and Diatribe. She is on X @MiriamETucker.