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

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.