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The adoption of the new “clinical obesity” definition alters prevalence estimates of obesity in many parts of the world compared with BMI-based definitions, new data suggested.

In January 2025, a Lancet Commission proposed that the diagnosis of obesity first be made via confirmation of excess adiposity using measures such as waist circumference or waist-to-hip ratio in addition to BMI. Next, a clinical assessment of signs and symptoms of organ dysfunction due to obesity and/or functional limitations determines whether the individual has the disease “clinical obesity” or “preclinical obesity,” a condition of health risk but not an illness itself.

That definition, although endorsed by more than 75 professional medical organizations, has proved controversial, with a commonly cited concern that people in the “preclinical obesity” category might be denied needed care. But the Lancet authors counter that the “preclinical” obesity category should be treated as a health risk factor, no differently than hypertension or dyslipidemia.

A new analysis of nationally representative surveys from 56 mostly low- and middle-income countries (LMICs) showed that application of a modified version of the “clinical obesity” definition would reduce obesity prevalence by more than 50% in some regions. It was published on July 24, 2025, in PLOS Global Public Health.

“Our results emphasize the need to carefully consider how obesity is defined in population surveillance to ensure its relevance to health outcomes. While the clinical obesity framework offers a more precise measure of obesity-related disease burden, its implementation in routine surveillance will require further adaptation to overcome data availability challenges,” the authors wrote.

Lead author Rodrigo M. Carrillo-Larco, MD, PhD, of the Department of Global Health at Emory University, Atlanta, told Medscape Medical News that there is a need for “agreement on whether the definition has to change and for what purposes so that the right tools and specific definitions are in place. If for clinical purposes, what definition should be used to start pharmacologic treatment, for claims and reimbursement, and for risk stratification of other diseases?”

In the paper, Carrillo-Larco and colleagues express the concern that with the new definition, “there is little to no opportunity for primary prevention of clinical obesity, as its definition already includes a cardiometabolic condition that most likely warrants secondary prevention or treatment.”

However, Lancet Commission Chair Francesco Rubino, MD, professor and chair of metabolic and bariatric surgery at King’s College London, London, England, told Medscape Medical News that this perception is incorrect. “Clinical obesity represents only a subset of the broader obesity spectrum. Total obesity prevalence should include both clinical and preclinical obesity.”

Added Lancet Commission member Ricardo Cohen, MD, director of the Center for Obesity and Diabetes, Oswaldo Cruz German Hospital, São Paulo, Brazil, “The published paper demonstrates that prevalence estimates shift because the clinical definition targets those with higher medical need and not because fewer people require care. This is about better risk stratification, not exclusion.”

Clinical Obesity Prevalence Differs From BMI-Only Obesity

The study included nationally representative data from the World Health Organization’s STEPS Survey for a total of 142,250 people in 56 countries in six world regions, including Africa (n = 49,438 from 18 countries), the Americas ( n = 3083 from one country), the Eastern Mediterranean (n = 19,292 from nine countries), Europe (n = 17,536 from seven countries), Southeast Asia (n = 27,334 from six countries), and the Western Pacific ( n = 25,567 from 15 countries).

Carrillo-Larco told Medscape Medical News that LMICs were sampled because “obesity may impose a greater burden in LMICs, given the limitations in access to treatment and counseling for obesity as well as for related comorbidities.”

The clinical obesity definition used for the study included objective measures of weight, height, waist circumference, blood pressure, fasting plasma glucose, and total cholesterol. The Lancet definition includes a longer list of conditions, but the authors note that those data are not routinely available in many LMICs. Rubino said this could lead to an underestimate of the true prevalence of obesity. On the other hand, Carrillo-Larco and colleagues noted that the lack of such data in many countries represents a limitation of the definition.

At the national level, the prevalence of clinical obesity in men ranged from less than 1% in Timor-Leste, Rwanda, Malawi, Ethiopia, Eritrea, and Cambodia to 29% in American Samoa, the Cook Islands, and Tokelau. In women, clinical obesity prevalence was as low as ≤ 1% in Vietnam, Timor-Leste, Rwanda, Ethiopia, Eritrea, and Cambodia, and as high as 28% in American Samoa and Tuvalu.

Among men, the age-standardized prevalence of clinical obesity was < 10% in 41 countries, mostly in Africa (18/41). Among women, the age-standardized prevalence of clinical obesity was less than 10% in 30 countries, also mostly in Africa (14/30). The largest shift in prevalence occurred in Malawi, with BMI-only obesity in 0.7% vs clinical obesity in 0.2%, a relative reduction of 67.7%. However, the absolute change was less than 1 percentage point.

Countries experiencing both a relative change of ≥ 10% and an absolute change of ≥ 10 percentage points were Nauru (-35.5% relative change and 13.3 percentage points in absolute change; prevalence of clinical obesity was 24.2% and that of BMI-only obesity was 37.5%) and Qatar (-49.2% and 10.3; prevalence of clinical obesity was 10.6% and that of BMI-only obesity was 20.9%).

In women, the relative change in prevalence exceeded 50% in Malawi (relative reduction of 52.8%; 5.6% for BMI-only obesity and 2.6% for clinical obesity) and Rwanda (-52.4%; 2.7% for BMI-only obesity and 1.3% for clinical obesity). In Malawi and Rwanda, the absolute change was 2.9 and 1.4 percentage points, respectively.

Countries with both relative and absolute changes exceeding 10% and 10 percentage points, respectively, were in the Western Pacific (American Samoa, Nauru, Niue, Samoa, Tokelau, and Tuvalu).

Rubino told Medscape Medical News, “Distinguishing clinical from preclinical obesity doesn’t reduce urgency — it ensures timely treatment for those who need it and directs prevention toward those for whom it remains possible.”

Regardless, Carrillo-Larco said, “Clinicians should always consider obesity as a multifactorial condition for which nonpharmacologic conditions are very important and social determinants of health play a key role.”

The authors received no specific funding. Rubino declared having received 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 has also served (unpaid) as a member of the scientific advisory board for Keyron and as a member of the data safety and monitoring board for GI Metabolic Solutions. Cohen declared having received research grants from Johnson & Johnson and Medtronic; honoraria for lectures and presentations from Johnson & Johnson, Medtronic, and Novo Nordisk; and serving on scientific advisory boards for Morphic Medical, Johnson & Johnson, and Medtronic.

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 at @MiriamETucker and on BlueSky at @miriametucker.bsky.social.