From compartments to dynamic physiology: toward actionable body composition

The 12th International Symposium on In Vivo Body Composition Studies (ISBCR 2025) highlighted a fundamental transition from estimating static tissue compartments to dynamic physiological phenotyping, actionable interpretation, and demonstrable value for clinical decision-making, health prediction, and human performance assessment. This represents an evolution in technological capability and conceptual framing, as an extension of the Functional Body Composition concept. Classical multicompartment models and established methods such as dual-energy X-ray absorptiometry, isotope dilution, bioimpedance, computed tomography, and magnetic resonance imaging remain foundational; however, emerging approaches increasingly integrate advanced imaging, artificial intelligence, bioimpedance spectroscopy, stable isotope methods, wearable sensing, and multidimensional phenotyping. Several themes were prominent at ISBCR 2025, including expansion of imaging beyond traditional DXA paradigms, increasing emphasis on muscle quality and fluid compartments, greater attention to visceral and ectopic adipose tissue, clinical applications in oncology and critical illness, the evaluation of obesity pharmacotherapy, the importance of generalizability to individuals across sex and ethnicity, and data governance. This perspective proposes a framework for future research in which body composition measurements become integral components of predictive models of health, performance, and physiological resilience. Future body composition assessment practices must include demonstrated added value over previous methods, and the greatest advances will come from technologies that bring physiologically meaningful assessment to large populations. The success of future technologies should be judged less by how precisely they estimate tissue compartments than by how effectively they improve physiological understanding, prediction, and decision-making.