ASSESSING ENERGY REQUIREMENTS AND BODY COMPOSITION: IMPLICATIONS FOR CLINICAL PRACTICE

Paediatric obesity arises as a result of a positive energy balance. A positive energy balance may be due to a reduced energy expenditure or increased energy intake. The reduced energy expenditure is often due to a reduced energy cost of activity, but a reduction in energy expenditure at rest can sometimes occur. In some disease states, such as Duchenne muscular dystrophy, energy imbalance may be a result of a decrease in resting energy expenditure, due to alterations in body composition, or energy metabolism. Regardless of the aetiology, the basis of dietary prescription to create an energy deficit relies on the accurate assessment of energy requirements. The use of the doubly labelled water method to measure total energy expenditure, and in turn, energy requirements, is impractical and costly in a clinical setting. As a result, predictive equations and self-reported measures of physical activity and energy intake, to establish baseline energy requirements, are frequently used. Current equations are based on data obtained from healthy paediatric populations, and the use of such equations to estimate energy requirements in populations whom differ from the norm are yet to be established. Furthermore, the accurate assessment of body composition is vital for evaluating and monitoring the success of various management programmes. While many body composition analysis techniques were developed in healthy adult populations, the use of these techniques in clinical, paediatric populations is questionable. To provide an insight into these issues, this thesis explored the assessment of energy requirements and body composition in two different paediatric cohorts (obese children and adolescents, and ambulatory boys with Duchenne muscular dystrophy). Additionally, the feasibility of a reduced dose of isotopes in the doubly labelled water technique was assessed in a cohort of healthy control children