Redefining Obesity Risk for Heart Failure: Incorporating Morbidity Into the 2024 EASO Framework Definition of Obesity

Conventional BMI-based obesity classification fails to capture the metabolic heterogeneity underlying obesity-related heart failure (HF) risk. We evaluated the 2024 European Association for the Study of Obesity (EASO) framework-which integrates central adiposity with medical, functional, and psychological morbidity-to refine HF risk stratification.

Among 449,550 UK Biobank participants (median follow-up 15.5 years), we applied three obesity definitions: (1) BMI ≥ 30 kg/m²; (2) the EASO framework, which retains the normal-weight category (BMI 18.5-< 25 kg/m²) and reclassifies individuals with BMI 25-< 30 kg/m² into 'EASO overweight' (WHtR < 0.5 and/or absence of morbidity) or 'EASO new obesity' (WHtR ≥ 0.5 plus ≥ 1 morbidity), while those with BMI ≥ 30 kg/m² are classified as BMI obesity regardless of morbidity status; and (3) an extended EASO framework that additionally stratifies individuals with BMI ≥ 30 kg/m² by morbidity status. Morbidity was defined per the 2024 EASO consensus criteria as the presence of ≥ 1 medical, functional, or psychological conditions associated with excess adiposity. Cox proportional hazard models estimated hazard ratios (HRs) for incident HF.

The EASO framework reclassified 15.6% of conventionally overweight individuals as obese, increasing the obesity prevalence from 24.5% to 40.1%. Compared with normal-weight individuals, the EASO overweight group (BMI 25-< 30 kg/m² without central adiposity or morbidity) exhibited the lowest HF risk (HR 0.84, 95% CI 0.80-0.89), confirming that overweight per se confers no excess risk in the absence of morbidity. By contrast, EASO new obesity (BMI 25-< 30 kg/m² with central adiposity and ≥ 1 morbidity; HR 1.32, 95% CI 1.25-1.39) demonstrated that morbidity presence-not BMI threshold-drives elevated HF risk within the overweight range. BMI obesity (BMI ≥ 30 kg/m²) yielded the highest summary HR (1.62, 95% CI 1.53-1.71), reflecting its compositional enrichment with high-morbidity individuals rather than superior risk discrimination. In the extended framework, morbidity status produced a consistent vertical upward shift in HF risk across all adiposity categories, establishing phenotypic characterisation beyond anthropometric thresholds as the key determinant of HF vulnerability.

The EASO framework refines HF risk stratification by uncovering morbidity-driven vulnerability within the overweight range that BMI alone obscures. The extended framework further demonstrates that morbidity status-rather than anthropometric thresholds-is a primary modifier of HF risk across all adiposity categories, supporting a shift from purely anthropometric toward phenotype-based obesity classification in cardiovascular risk assessment.