Preliminary studies of energy expenditure in infants under six months of age.

In the study energy expenditure measurements have been made by open circuit calorimetry on a number of occasions on four infants, with special reference to the energy cost of resting metabolism, activity and diet-induced thermogenesis. In addition, for two subjects the energy cost of growth was determined. The energy expended with respect to activity was highly variable among all subjects and it was postulated that this was a factor of great importance in the energy balance of young infants; indeed, the effect of diet-induced thermogenesis was enhanced by activity. A calculation of the total energy required to gain 1 g of wet tissue in two infants was found to be different. As their intakes were 'low' and 'high' though their weight gains were accelerated and slow respectively, the difference in the energy cost of growth has been discussed as a reason for this paradox.