TOTAL-ENERGY EXPENDITURE AND BODY-COMPOSITION IN EARLY INFANCY

In adults greater energy expenditure, primarily on physical activity, is associated with greater leanness. Such an association has proved mo re difficult to demonstrate in infants, partly due to the difficulty o f measuring fatness and free living energy expenditure in this age gro up. Stable isotope techniques now make such investigations more viable . Objective-The relationship between body composition and energy expen diture was investigated in 12 week infants. Methods-Total energy expen diture and fat mass were estimated using the doubly labelled water tec hnique. Subjects-92 normal healthy infants. Results-Fat mass was corre lated with both triceps and subscapular skinfold thicknesses (p < 0.00 1). After controlling for body size, age was a significant predictor o f fat mass (p = 0.003), whereas total energy expenditure was not (p = 0.463). Conclusions-The cross sectional link between activity level an d fatness in young infants, reported previously, does not persist when energy expenditure is considered.