Ann Intern Med
Clinical obesity often hides behind a normal BMI
Clinical takeaway: Waist circumference and related body measures may help flag obesity-related organ dysfunction in patients whose BMI looks normal.
BMI offers little information about whether excess fat has begun to harm organ function. To close that gap, last year the Lancet Diabetes & Endocrinology Commission proposed the notion of "clinical obesity," which pairs anthropometric evidence of excess adiposity with signs of reduced organ or physical functioning. How often that picture appears across BMI classes had not been quantified previously in nationally representative data.
About one in four adults with a normal BMI met criteria for clinical obesity, as did roughly half of those who were overweight, well below the conventional obesity threshold. Clinical obesity here meant excess adiposity by body measurement plus at least one sign of organ or functional impairment: elevated blood pressure, abnormal glucose or lipids, liver fibrosis on elastography, reduced kidney function, or difficulty with mobility and self-care. Adjusted prevalence climbed with BMI class, from 26% at normal weight to 50% at overweight and 85% at the most severe obesity tier.
Excess adiposity was defined by three body measures: waist circumference, waist-to-hip ratio, and waist-to-height ratio. Using two or three abnormal measures regardless of BMI identified 78% of adults as having excess adiposity, nearly double the 41% flagged by abnormal BMI plus a single abnormal measure. The broader anthropometric net catches many people that a BMI-anchored screen would clear.
The study drew on 5,642 U.S. adults in the 2021–2023 National Health and Nutrition Examination Survey (NHANES) cycle. The survey lacks the detailed clinical data to fully operationalize the Commission's proposal, which the authors say likely underestimates true prevalence. The definition itself rests on expert opinion and has not been validated against outcomes.
Current screening and treatment thresholds, including those for incretin therapies, anchor to BMI, so a shift toward anthropometric criteria would widen the pool of patients considered for evaluation. The authors frame this as a case for adding waist-based measures to risk assessment.
“Many people assume that if their BMI says they are not obese, they don’t have to worry about the many health problems linked to obesity,” said Brian Lee, MD, MAS, a hepatologist and liver transplant specialist with Keck Medicine and principal investigator of the study. “Our findings show that millions of Americans may already have obesity-related health impacts and may be missing needed health interventions.”
Source: Elhence H. Ann Intern Med. 2026 Jun 2. National prevalence of clinical obesity by BMI class: a national cross-sectional study