Invited State of the Art Review for MCP Rethinking Obesity Beyond Body Mass Index: A Review of Body Composition and Chronic Disease Risk.

Body mass index (BMI) is widely used to diagnose obesity and assess chronic disease risk, yet it does not reflect true body composition (BC), particularly fat distribution and lean mass. While widely used and valuable for population-level screening, BMI is limited in its ability to capture individual-level variations in BC and disease risk. We aimed to critically evaluate the limitations of BMI and highlight the clinical value of incorporating BC metrics in obesity diagnosis and risk stratification. This narrative review with a structured literature search synthesized evidence from observational studies, clinical cohorts, and imaging-based analyses published between January 1, 2000 and December 31, 2025. Searches were conducted using PubMed, Scopus, Web of Science, and Google Scholar using predefined keywords related to BC, adiposity, and chronic disease risk. Although a structured search strategy was employed, this review did not follow formal systematic review methodology (eg, PRISMA) and instead emphasizes qualitative synthesis of evidence to compare BMI with direct measures across chronic diseases. Individuals with normal BMI but high visceral fat are at increased risk for conditions such as type 2 diabetes, cardiovascular disease, and cancer. Conversely, high-BMI individuals with healthy BC profiles may have better outcomes. Phenotypes such as sarcopenic obesity and normal-weight obesity are poorly identified using BMI alone. Imaging tools like dual-energy X-ray absorptiometry and bioelectrical impedance analysis offer more precise risk assessment. We conclude a shift from BMI-centric approaches to personalized BC-based evaluation is essential for improving obesity diagnosis, guiding interventions, and reducing chronic disease burden.