Beyond BMI: Integrating Gut Microbiota, Skeletal Muscle Health, and Ecological Complexity into Assessment of Human Metabolic Health

ABSTRACT BACKGROUND Body mass index (BMI) remains one of the most widely used anthropometric measures for classifying body weight status and estimating health risks at the population level [1,3]. However, BMI does not capture substantial interindividual variability in body composition, adiposity distribution, skeletal muscle function, and other biological determinants of metabolic health [6-8]. OBJECTIVE/HYPOTHESIS We hypothesize that body mass index (BMI) is a biologically incomplete marker of human metabolic health because it provides limited information about body composition, adiposity distribution, and other determinants of metabolic function [6,8]. We propose that metabolic resilience may be better understood through a Thomas DM, Bredlau C, Bosy-Westphal A, Mueller M, Shen W, Gallagher D, Maeda Y, McDougall A, Peterson CM, Ravussin E, Heymsfield SB. Relationships between body roundness with body fat and visceral adipose tissue emerging from a new geometrical model. Obesity (Silver Spring). 2013;21(11):2264-71. doi: 10.1002/oby.20408. Epub 2013. PMID: 23519954; PMCID: PMC3692604. develops a broader conceptual framework for understanding metabolic heterogeneity. This framework considers potential interactions among body composition, skeletal muscle function, gut microbiota, microbial metabolites, inflammatory pathways, and environmental determinants beyond conventional anthropometric classification [810,13,16-18,37,39,54,55]. CONCLUSIONS Although BMI remains a valuable epidemiological measure and clinical screening tool, it should be interpreted within a broader biological context rather than used as a standalone indicator of metabolic health. Integrating body composition, skeletal muscle health, gut microbiota ecology, microbial metabolite signaling, and environmental determinants into systems-based models may provide a more comprehensive framework for understanding metabolic resilience and informing risk assessment and precision medicine [13,16-18,37,72].