ADJUSTING MILK INTAKE FOR BODY-SIZE IN EARLY INFANCY

Energy intake and expenditure are related to body size and body compos ition and therefore must be taken into consideration when comparing in dividuals. Previous work has typically expressed energy metabolism var iables per kilogram body weight or per kilogram fat-free mass. However this may not remove the effect of body size entirely. In infancy milk volume intake is usually expressed in a similar manner which may not be entirely appropriate. The most appropriate method of expressing mil k volume intake relative to body weight and fat-free mass was investig ated in 20 normal breast-fed infants at 6 weeks of age. Regression ana lysis revealed that the relationship between milk intake and body weig ht could be adjusted for by expressing milk intake per kg(0.68), and t hat the relationship between milk intake and fat-free mass could be ad justed for by expressing milk intake per kg(0.54). These values are no t significantly different to 0.50 which is the square root of body wei ght. It is suggested that in studies of energy metabolism in infancy t he expression of milk intake per kg(0.50) should be used as the most a ppropriate adjustment for removing the influence of body size upon mil k intake, in the first few months of life.