Energy intake, appetite and body mass in infancy

Energy intake in infancy depends on the infant's appetite, which, in turn, depends to a considerable extent on the infant's size, as size is an import ant determinant of energy expenditure. Previous work on six-week old breast -fed infants has suggested that, at this age, milk intake in infants is pro portional to the square root of body weight (wt.(0.5)). In this paper, the form of the relationship between body weight and energy intake is examined in infants of different ages, using data from two longitudinal studies, one of initially breast-fed and one of initially bottle-fed infants. In the fi rst data set, energy intake is proportional to body weight raised to powers ranging from 0.63 to 1.23 at different ages and, in the second, to body we ight raised to powers ranging from 0.50 to 1.07 at different ages. No singl e value is consistent with all the data at all ages. In general, the powers decrease up to six months of age, and then increase again, a pattern that may be due to the pattern of changes in the adiposity of the infants, as re flected in their body mass indexes (BMIs). (C) 1999 Elsevier Science Irelan d Ltd. All rights reserved.