Obesity is a major cause of disability and premature death globally, sparking debate about whether it should be classified as a disease or a risk factor. A recent proposal in The Lancet Diabetes & Endocrinology introduced a framework distinguishing preclinical obesity from clinical obesity, advocating BMI-based identification of obesity confirmed by additional body fat measures. Individuals with organ dysfunction or functional limitations are classified as having clinical obesity, and those without such complications are considered preclinical. Although this approach aims to improve risk assessment and treatment methods while reducing the stigma, its practical applicability and implications for cardiometabolic diseases remain uncertain. It also raises questions regarding the necessity of additional confirmation measures and the impact of lifestyle modification on clinical obesity status.
The aim of this study was to assess whether BMI-based obesity needs confirmation by additional anthropometric measures. To estimate the prevalence of preclinical and clinical obesity in nationally representative and population-based cohorts, and to assess their associations with type 2 diabetes (T2D) and cardiovascular disease (CVD). It also assessed remission of clinical obesity following structured lifestyle intervention and detected predictors of remission.
Data were analysed from three complementary studies: U.S. National Health and Nutrition Examination Survey (NHANES 2017-2018), the European Prospective Investigation into Cancer and Nutrition (EPIC)-Potsdam cohort in Germany, and Tübingen Lifestyle Intervention Program (TULIP). NHANES gives cross-sectional, nationally representative data on 5,265 U.S. adults aged 20 years or older, which include detailed anthropometry, dual-energy X-ray absorptiometry (DXA) body fat measurements, metabolic biomarkers, blood pressure, kidney and liver function marker and self-reported health information.
EPIC-Potsdam is a prospective cohort of over 27,000 German adults followed for incident T2D and CVD. A random subcohort was used to estimate obesity classifications and assess disease risk using Cox regression models. TULIP is a prospective and uncontrolled lifestyle intervention study in high-risk individuals in Germany, from which 150 participants with BMI ≥30 kg/m² and complete clinical obesity data were included to examine changes in obesity classification after 9 months of diet and exercise counseling.
Obesity was defined using ethnic-specific BMI thresholds and confirmed by waist circumference, waist-to-hip ratio, waist-to-height ratio, or DXA-based body fat percentage. Clinical obesity was defined by the presence of obesity-related dysfunction across cardiovascular, metabolic, renal, respiratory, hepatic, musculoskeletal, urinary, or functional domains based on available data in each cohort.
Results showed that nearly all adults with BMI-defined obesity were confirmed as having excess adiposity by at least one additional anthropometric measure in both NHANES and EPIC-Potsdam. This suggests that mandatory confirmation adds limited practical value. In NHANES, 82.6% of adults with confirmed obesity met at least one criterion for clinical obesity, corresponding to a population prevalence of 36.0% for clinical obesity and 7.6% for preclinical obesity. The proportion classified as clinical increased with age and BMI category and was similarly high in sexes and major racial/ethnic groups. Comparable patterns were observed in EPIC-Potsdam despite a lower prevalence of severe obesity. Most individuals with clinical obesity met multiple overlapping criteria, specifically cardiovascular components like hypertension.
Clinical obesity was strongly linked to a higher risk of incident T2D (hazard ratio ~7.9) and CVD (hazard ratio ~2.8) as compared with individuals without obesity and without clinical criteria. Elevated risk was also observed in individuals without obesity who met clinical criteria, and preclinical obesity conferred increased T2D risk but not CVD risk. The Commission’s strict metabolic definition—requiring simultaneous hyperglycemia, elevated triglycerides, and low HDL cholesterol—classified many individuals with obesity-related metabolic dysfunction as preclinical, despite their elevated cardiometabolic risk. Using alternative metabolic definitions substantially increased the proportion categorized as clinical obesity.
In the TULIP intervention, participants achieving more than 3% weight loss showed a reduction in clinical obesity prevalence from 71% to 57%, with remission observed in a subset. Improvements were most pronounced in metabolic components, specifically triglycerides and prediabetes. Younger age and lower liver fat content, rather than baseline BMI or magnitude of weight loss, predicted remission, which highlights the importance of ectopic fat distribution.
In summary, nearly all individuals with BMI-defined obesity met additional anthropometric criteria for adiposity, and the majority fulfilled criteria for clinical obesity. Clinical obesity was strongly linked to future T2D and CVD risk, while the current strict metabolic definition may underestimate obesity-related dysfunction. Moderate lifestyle-induced weight loss can induce remission of clinical obesity independent of baseline BMI, with liver fat playing a key predictor. These findings suggest that the proposed framework effectively identifies high-risk individuals; however, refinement of diagnostic criteria, specifically metabolic components, is necessary to better capture risk heterogeneity and optimize treatment strategies in the obesity population.
Reference: Schiborn C, Hu FB, Stefan N, et al. Preclinical and clinical obesity: prevalence, associations to cardiometabolic risk and response to lifestyle intervention in NHANES and the EPIC-Potsdam and TULIP studies. Nat Commun. 2026;17:1935. doi:10.1038/s41467-026-69738-w
