Body Composition in Heart Failure: A Phenotype-Informed Framework for Assessment and Management.

Body mass index (BMI) and waist-based anthropometric indices are widely used to estimate adiposity and cardiometabolic risk. Yet in established heart failure (HF), modestly higher BMI is associated with improved survival, while waist-based measures show a linear association with worse outcomes. This apparent discrepancy suggests that the biological interpretation of BMI and body composition changes once HF develops. In HF, BMI reflects the composite of adipose tissue, fluid accumulation, and skeletal muscle wasting, whereas waist-based indices primarily reflect central adiposity. In this narrative review, we explore the challenges of body composition interpretation in HF and propose a conceptual, phenotype-informed framework for body composition assessment and management. Within this framework, BMI may mask biologically distinct yet clinically relevant phenotypes defined by adiposity, congestion, and skeletal muscle integrity. By integrating these interacting components, the framework highlights that similar BMI values may represent biologically distinct phenotypes with different risk profiles and potential management implications. Across BMI categories, preserved muscle mass and limited congestion are associated with more favorable outcomes, whereas central adiposity, congestion, and muscle wasting identify higher-risk states. This conceptual framework provides a foundation for future research and may ultimately inform more individualized body composition assessment, risk stratification, and management of patients with HF.