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Conference on 'Nutrition at key life stages: new findings, new approaches'
Symposium 4: Clinical nutrition: gold standards and practical demonstrations
16-19 June 2015
The Nutrition Society Irish Section Meeting
the University College Cork, Cork
In vivo body composition analysis (BCA) is within the centre of integrative physiology on understanding the body responses to internal and external factors at different biological levels. BCA applies concepts of cellular/molecular physiology, biochemistry and experimental approaches to understand the function at the level of whole body or its individual organs and tissues. Within clinical nutrition BCA is used to identify obese patients and malnutrition, to characterize weight gain and weight loss and to diagnose sarcopenia (i.e. a reduced quantity of skeletal muscle) and cachexia (i.e. involuntary weight loss and underweight). BCA is part of cardio-metabolic risk assessment and adds to characterize hyper- and dehydration, development and growth, ageing as well as physical performance. In contrast to BCA crude estimates of the nutritional status such as BMI and waist circumference inadequately characterize nutritional status, health risks and morbidity(1-6). Thus, BMI and waist circumference cannot provide a sound basis for nutritional assessment, understanding physiology of metabolism, clinical decision making, personalized medical nutrition, prediction of prognosis in patients and for in depth biomedical research.
Basic models
Body composition is about models and methods(7). About 70 years ago, the science of BCA started with the classical 'two component model', i.e. dividing the body into two major compartments, fat free mass (FFM; includes cellular water within adipocytes) or lean soft tissue (LST; the sum of all lean compartments, organs and tissues, also includes non-fat lipids; also called lean body mass) and fat mass (FM; Fig. 1). FFM includes total body water, bone minerals and protein. FM refers to chemical fat i.e. energy stores with TAG accounting for about 80 % of adipose tissue. Present models of body composition refer to 'five different levels', that is, 'atomic' (including the eleven major elements, H, O, N, C, Na, K, Cl, P, Ca, Mg, S), 'molecular' (including six components, lipid, water, protein, carbohydrates, bone minerals, soft tissue minerals), 'cellular' (that is, three or four components, cell mass, extracellular fluids, extracellular solids, where cell mass can be divided into...