The lancet commission definition of clinical obesity: a multi-cohort cross-sectional analysis from early childhood to older age in seven high-income countries

Background The Lancet Diabetes & Endocrinology Commission on Clinical Obesity established a consensus definition for clinical obesity (excess adiposity with clinical or laboratory evidence of adiposity-related sequelae). In contrast to body mass index (BMI)-based criteria, this new definition conceptualises obesity as a chronic disease to guide prevention and management. We sought to determine the age-specific cross-sectional prevalence of clinical and BMI-defined obesity from early childhood to older age. Methods We analysed 11 population-derived childhood and adult cohorts in Australia, Canada, Estonia, Finland, the Netherlands, UK, and US ( n = 786,557) from 1996 to 2023. Cross-sectional prevalence of BMI-defined (using Centres for Disease Control and Prevention cut-points) and clinical obesity was calculated for each age group across cohorts, stratified by sex and education level. Findings No cohort captured all diagnostic criteria for clinical obesity. Using available heterogeneous data spanning different epochs, the cross-sectional prevalence of clinical obesity (range 2.1–4.9%) was lower than BMI-defined obesity (7.0–10.8%) in childhood and adolescence, increased across adulthood, surpassed BMI-defined obesity prevalence in mid-to-late adulthood, and peaked at 65–74 years (52.0% vs. 34.4% for BMI-defined obesity). Clinical obesity prevalence was higher in men compared to women in early-to-mid adulthood (e.g. 18.6% vs. 13.9%, respectively at 35–44 years), and higher in women later in adulthood (e.g. 44.1% vs. 57.1%, respectively at 65–74 years). Clinical obesity was marginally less prevalent in the highest education group (range 1.3–48.2%) compared to the lowest (3.6–55.0%). Interpretation We provide population-level cross-sectional prevalence data on clinical obesity, which were largely consistent across diverse high-income settings. The findings highlight challenges in operationalising the Commission's conceptual definition in epidemiological studies using large-scale, incomplete and heterogeneous real-world data. Population data capturing all diagnostic criteria of clinical obesity are essential to further improve the understanding of the prevalence and translational implications of these definitions. Funding No study-specific funding to declare.