Lancet Commission Redefines Obesity, Drawing Criticisms from Some Professional Groups

Two leading obesity organizations have voiced concerns about a recent redefinition of obesity by the Lancet Commission, but the commission’s lead author maintains that these concerns are largely based on misinterpretations.

New Obesity Definition and Diagnosis Process

On January 14, 2025, the Lancet Commission introduced a new definition of obesity. This definition categorizes obesity into two major types: “clinical obesity,” considered a disease, and “preclinical obesity,” considered a health risk factor. According to the commission, obesity should initially be diagnosed through measurements such as waist circumference, waist-to-hip ratio, or body mass index (BMI). The presence or absence of organ dysfunction or functional limitations further classifies it as clinical or preclinical.

Support and Endorsement

The commission, chaired by Francesco Rubino, MD, professor and chair of Metabolic and Bariatric Surgery at King’s College London, UK, published its report in Lancet Diabetes & Endocrinology. It received endorsements from over 75 medical organizations including the Association of British Clinical Diabetologists, American Association of Clinical Endocrinologists, American Diabetes Association, American Heart Association, the Obesity Society, and the World Obesity Federation, among others.

Commission’s Perspective on Criticisms

Dr. Rubino addressed criticisms in an interview with Medscape Medical News. He clarified that the commission did not propose delaying diagnosis until clinical manifestations are present. Instead, the differentiation between preclinical and clinical obesity serves to distinguish diseases directly caused by obesity from potential future risks, much like how polyps and benign tumors are distinguished from cancer.

Concerns from Obesity Medical Association (OMA)

The OMA expressed significant concerns about potential unintended consequences of this framework, including the risk of redefining obesity from a disease to a mere risk factor. The commission, however, clearly defined “preclinical obesity” as a risk factor and “clinical obesity” as a chronic disease.

The OMA worried that classifying individuals as preclinical might exclude them from insurance coverage for weight management treatments such as medications, behavioral therapies, and surgical interventions.

Response to Concerns from EASO

The European Association for the Study of Obesity (EASO) had also voiced concerns that the commission suggested type 2 diabetes (T2D) does not necessitate obesity treatment. Dr. Rubino refuted this claim, indicating that the report explicitly stated that treating both preclinical and clinical obesity is essential for managing T2D.

Focus and Intent of the Commission

Dr. Rubino emphasized that the commission’s primary focus was not on providing new treatment guidelines, but rather on refining diagnostic criteria. He highlighted that confusing diagnostic criteria with management frameworks overlooks the main intent of the commission’s work.

Commission’s Vision for Future Dialogue

Dr. Rubino acknowledged the need for ongoing dialogue surrounding the commission’s conclusions. He emphasized that the scientific debate should remain grounded in accurate representations of the commission’s conclusions.

“We understand that we are proposing a significant shift in how we diagnose and conceptualize obesity,” Dr. Rubino concluded. “It is only natural for such a report to prompt questions and thoughtful critiques, and we welcome the opportunity to engage in constructive discussions as part of a healthy academic dialogue… However, it is essential that the scientific debate remains grounded in accurate representations of our Commission’s conclusions.”

Conflict of Interest Disclosure

Dr. Rubino declared receiving research grants from Ethicon (Johnson & Johnson), Novo Nordisk, and Medtronic; consulting fees from Morphic Medical; and speaking honoraria from Medtronic, Ethicon, Novo Nordisk, Eli Lilly, and Amgen. He also served (unpaid) as a member of the scientific advisory board for Keyron, a member of data safety and monitoring board for GI Metabolic Solutions, president of the Metabolic Health Institute (nonprofit), sole director of Metabolic Health International, and London Metabolic and Bariatric Surgery (private practice).

Author Bio

Miriam E. Tucker is a freelance journalist based in the Washington DC area. She regularly contributes to Medscape Medical News and has work appearing in the Washington Post, NPR’s Shots blog, and Diatribe. She is on X @MiriamETucker and BlueSky @miriametucker.bsky.social.

Final Thoughts and Call to Action

The Lancet Commission’s redefinition of obesity aims to clarify diagnostic criteria and improve disease management. While some professional organizations have raised concerns, the commission maintains that its recommendations are crucial for personalized care and effective treatment approaches.

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