Critics Misunderstand Lancet Obesity Definition, Author Says

Two professional obesity organizations have expressed concerns about the Lancet Commission’s new obesity definition, but its lead author says that much of the concern reflects misinterpretation. 

On January 14, 2025, the Lancet Commission redefined obesity by classifying it as either “clinical obesity,” a disease, or “preclinical,” a health risk factor. They recommended that obesity be first diagnosed via confirmation of excess adiposity using measures such as waist circumference or waist-to-hip ratio in addition to body mass index. Next, the presence or absence of signs and symptoms of organ dysfunction due to obesity and/or functional limitations determines whether the individual has “clinical” or “preclinical” obesity. 

The Commission was chaired by Francesco Rubino, MD, professor and chair of Metabolic and Bariatric Surgery at King’s College London, United Kingdom. The report was published in Lancet Diabetes & Endocrinology, with the endorsement of more than 75 medical organizations, including the Association of British Clinical Diabetologists, the American Association of Clinical Endocrinologists, the American Diabetes Association, the American Heart Association, the Obesity Society, the World Obesity Federation, and obesity and endocrinology societies from countries in Europe, Latin America, Asia, and South Africa.

However, not all professional obesity-related organizations signed on. Two that did not, the European Association for the Study of Obesity (EASO) and the Obesity Medicine Association (OMA), have now released statements critical of the Lancet report. Both raise multiple concerns, but common to both is the fear that people in the “preclinical obesity” category could be denied needed care. 

The EASO, which published its own obesity “framework” in July 2024, said the Lancet Commission report “introduces problematic concepts that could potentially harm patient care.” The “preclinical obesity” category, they said, “suggests a watchful waiting strategy that could delay crucial early interventions, increase health risks for children, adolescents, and adults, and potentially worsen long-term health outcomes… Unlike diabetes or osteoporosis, where early diagnosis and prevention are standard, the Lancet Commission criteria proposes waiting for clinical manifestation of obesity-related complications.”

This is inaccurate, Rubino told Medscape Medical News. “The commission does not propose to wait for clinical manifestations of obesity… Defining clinical manifestations of the illness directly caused by obesity does not equate to a recommendation to wait until disease develops, in the same way as distinguishing a polyp from cancer does not equate to a recommendation to wait for progression to cancer.”

Along similar lines, the OMA expressed “significant concerns about the potential unintended consequences of this framework, which risks redefining obesity from a disease to merely a risk factor.” In fact, the Commission defined “preclinical obesity” as a risk factor and “clinical obesity” as a chronic disease. 

The OMA said, “by fragmenting obesity into preclinical and clinical categories, there is a real danger of excluding individuals classified as ‘preclinical’ from insurance coverage for essential medical weight management treatments, including medications, behavioral therapies, and surgical interventions.” 

According to Rubino. “The Commission did not recommend excluding people with preclinical obesity from coverage of weight management treatments. Instead, we say that ‘preclinical obesity is associated with a variable but generally increased risk’ and ‘the type of intervention…should be based on individual risk/benefit assessment, considering the severity of excess or abnormal adiposity and the presence or absence of other risk factors and coexisting obesity-related diseases or disorders.’” 

Moreover, he noted, “There is no evidence that accurate disease diagnosis leads to systematic gaps in coverage for treatments of conditions viewed as risk factors rather than diseases. Clinicians distinguish between prediabetes and diabetes, polyps and cancer, and other similar conditions, which does not affect coverage for effective early interventions. Treatment approaches differ between prediabetes and diabetes, as well as between polyps, HIV, and hypertension versus cancer, AIDS and cardiovascular disease. Accurate disease diagnosis is essential for personalized care.”

Rubino also refuted EASO’s claim that the Commission had suggested that “type 2 diabetes [T2D] does not necessitate obesity treatment.” In fact, the report says “Obesity (preclinical or clinical) can contribute to the development of T2D and adversely affect diabetes control and progression. For this reason, the treatment of both preclinical and clinical obesity should be part of the management of T2D.”

But, Rubino noted, “While some may have hoped for new treatment guidelines from the Commission, that was not our focus. Confusing diagnostic criteria with management frameworks misses the key intent of our work.”

He concluded, “We understand that we are proposing a significant shift in how we diagnose and conceptualize obesity. 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. We hope to be evaluated based on what we have said, rather than on misattributed statements.”

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 and serving (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); and the sole director of Metabolic Health International and London Metabolic and Bariatric Surgery (private practice). 

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 and BlueSky @miriametucker.bsky.social.