Prevalence and comorbidity burden of clinical obesity in US adults

BACKGROUND: This study aimed to estimate the prevalence and comorbidity burden of clinical obesity among US adults. METHODS: Analyzing data from 53,333 US adults (NHANES, 1999–2018), we stratified participants into no obesity, preclinical obesity, and clinical obesity based on BMI, waist circumference, and presence of organ dysfunction or functional limitations. Mortality risks were assessed via survey-weighted Cox proportional hazards regression, Fine-Gray subdistribution hazard model, and Kaplan–Meier curves. Latent class analysis (LCA) identified distinct comorbidity clusters. FINDINGS: Overall obesity prevalence rose from 46.7% to 61.7%, with clinical obesity (from 34.6% to 46.6%) constituting the dominant type. Clinical obesity was associated with significantly higher risks of all-cause (HR 1.46, 95% CI 1.29–1.66) and cardiovascular (HR 1.65, 95% CI 1.29–2.10) mortality versus preclinical obesity. Within clinical obesity, individuals with ≥ 5 comorbidities had an increased all-cause mortality 3.0-fold (25.4 vs 7.8 per 1000 person-years) and cardiovascular mortality 3.4-fold (5.1 vs 1.6 per 1000 person-years) compared to a single comorbidity. LCA revealed three distinct comorbidity clusters with prognostic heterogeneity; the renal dysfunction-dominant cluster exhibited the poorest survival. CONCLUSION: The expanding US obesity epidemic is predominantly characterized by a growing burden of high-risk clinical obesity, signifying a shift towards more severe disease phenotypes. Accurate comorbidity quantification in clinical obesity is crucial for refining prognostic assessment and optimizing treatment strategies.