Samenvatting

Muscle health, encompassing muscle mass, composition, strength, physical performance and patient-reported outcomes, is a key determinant of clinical outcomes across the life course and a wide range of disease states. Despite growing recognition of its importance, muscle health remains insufficiently integrated into routine clinical nutrition practice, and nutritional recommendations often rely on population averages rather than individual muscle status, disease phase or metabolic context.This narrative review, developed by an international multidisciplinary expert group, synthesises current evidence on muscle health and clinical nutrition across major clinical domains, including ageing, cancer, metabolic disease, obesity, weight loss interventions and acute illness. We critically appraise methods for assessing muscle mass, function, and patient-reported outcomes, highlighting their strengths, limitations, and feasibility for clinical practice and research. In doing so, we highlight marked heterogeneity in metabolic and functional responses to nutrition and exercise interventions, underscoring the need for phenotyping, endotyping and precision nutrition to individualise protein and energy requirements.Beyond biological mechanisms, we address key implementation challenges limiting translation into practice, including inequities in access to dietetic and other rehabilitation services, variability in health system organisation and underuse of functional and patient-centred outcomes in trials and routine care. Finally, we propose a translational research agenda to harmonise outcome measures, improve trial design and support integration of muscle health assessment and personalised nutritional strategies into clinical care pathways.By positioning muscle health as a central and actionable outcome of clinical nutrition, this review supports a shift from uniform recommendations towards more personalised and effective nutrition care.