Relative Fat Mass: Refining Adiposity Measurement in the Era Beyond Body Mass Index

Purpose of Review To position relative fat mass (RFM) as a more accurate, physiologically grounded, and clinically useful alternative to body mass index (BMI) for assessing adiposity and predicting cardiometabolic risk, including heart failure. Recent Findings RFM estimates body fat percentage using a sex-specific formula based on waist circumference and height. RFM not only correlates more strongly with fat mass than BMI, but also shows a weaker correlation with muscle mass. This distinction helps reduce lean mass-related confounding in the assessment of adiposity. In clinical studies, RFM has emerged as a robust predictor of incident heart failure, cardiometabolic disease, and all-cause mortality. Summary RFM avoids misclassification of adiposity in individuals with high muscle mass and better reflects abdominal adiposity than BMI. As the prevalence of heart failure and other obesity-related diseases continues to rise, RFM offers a practical and intuitive tool for assessment of adiposity and heart failure risk – challenging the long-standing dominance of BMI.