Energy expenditure of malnourished children during catch-up growth

Abstract

Refeeding strategies require knowledge of energy partitioning. By principles of energy balance, energy intake (Ei) is partitioned between maintenance (Em), activity (Ea), growth (Eg) and faecal and urinary losses (Ew). Energy requirements can thus be calculated as the sum of the components of the energy-balance equation (equation 1). Under anabolic conditions, Ei is equal to dietary Ei requirements. E, is partitioned between energy expended for tissue biosynthesis (Esyn) and energy stored as new tissue (Est). Both values vary according to the composition of weight gained. Since Em and E, cannot be easily separated, the sum Em+, is estimated. From estimates of normal growth in the reference infant, less than 15% of dietary E, is partitioned to E,, whereas during rapid catch-up growth, E, may be 50% or more of Ei. Reasonable estimates of Em+, and of E, would enable prediction of energy requirements for refeeding during accelerated weight gain. Energy expenditure for maintenance and activity, Em Based on the fact that all metabolizable energy is either expended or stored, one approach to estimating Em+, is regression of metabolizable energy intake (MEI; Y) on rate of weight gain (X). This assumes (1) no net deposition of tissue at zero weight gain and thus no energy partitioned to E,, (2) all energy expended at zero weight gain is for maintenance and activity which is estimated by the Y-intercept. The advantages of this approach are that estimates can be made independently of actual measurements of energy expenditure or of energy storage, particularly during recovery from malnutrition because of accelerated rates of weight gain. The accuracy of the estimates is limited, however, by the accuracy of dietary intake and faecal excretion values. A widely-cited estimate of Emfa, 343 kJ (82 kcal)/kg per d published by Spady et al. (1976), was actually the unweighted mean of three independent estimates of Em+,. The first was estimated as 358 kJ (85.5 kcal)/kg from the Y-intercept of the regression of ME1 v. rate of weight gain of sixteen subjects in the rapid-weight-gain phase of recovery from malnutrition. The second was 341 kJ (81.5 kcal)/kg, the Y-intercept of ME1 on weight gain or loss of four subjects in the acute phase of malnutrition and in negative energy balance. The third estimate was based on an assumed basal metabolic rate of 222 kJ (53 kcal)/kg, approximated in an independent study of other malnourished children (Ashworth, 1969a) and the assumption that Em+, is equal to 1.5 times basal metabolic rate. The latter approach estimated 335 kJ (80 kca1)kg as Em+,. We have made similar estimates (Table 1) from published values of dietary intake (Waterlow, 1961; Ashworth et al.