Validation of clinical and preclinical obesity across global cohorts

In 2025, a Lancet Commission proposed distinguishing clinical obesity, defined by adiposity-related organ dysfunction, from preclinical obesity, defined by excess adiposity with preserved function, and recommended using anthropometric measures beyond body mass index (BMI) to confirm obesity status 1 . Here we report the comparative performance of this framework versus conventional BMI-based classification using prevalence, incidence and mortality data from 844,108 adults across four cohorts in China, the UK, the USA and Spain. Complementing BMI with waist circumference and waist-to-height ratio data showed that BMI alone overestimated obesity in 1.2–3.1% and underestimated it in 5.2–8.6% of participants across cohorts. The combined anthropometric definition increased overall obesity prevalence by 3.3–7.4% relative to BMI-based classification. Clinical obesity accounted for 22.7–31.3% of total obesity, with an overall population prevalence of 5.6–10.9%. A large proportion of individuals (between 77.4% and 91.3%) with preclinical obesity at baseline showed no progression to clinical obesity over 10 years. Increased mortality risk was associated with the combined anthropometric definition of obesity, but not with BMI-only obesity. Clinical obesity was associated with substantially higher all-cause mortality (hazard ratio 1.69, 95% confidence interval 1.64–1.73), whereas preclinical obesity conferred only modest risk (1.19, 1.14–1.24). These findings support the global adoption of the Lancet Commission diagnostic framework to improve obesity care and policy.