COMMITTEE ON NUTRITION METHODS FOR DETERMININGCOMPOSITION OF THE HUMAN BODY With a Note on the Effect of Diet on Body Composition

born and adult are presented in Table I, both on a fresh-weight and a fat-free fresh weight basis. The latter basis for express ing values avoids discrepancies that arise because of alterations in fat content. It is evident that signfficant changes in body composition occur during growth. Water, sodium, and chloride contents decline, while contents of nitrogen, calcium, potas sium, magnesium and phosphorus all in crease. In these data, body fat content is not strikingly different in the two age groups. As will be discussed later, measure ments on living subjects reveal an increas ing adiposity in later adult life. The extensive observations of Widdow son and her @ @†̃¿ 12 have shown that growth changes occur in body compo sition of other mammalian species, changes that are comparable in magnitude and di rection to those of the human. These spe cies include the mouse, rat, cat, guinea pig, rabbit, and pig. It is entirely probable, therefore, that the trend of changes in body composition depicted in Table I represents a phenomenon common to all mammalian protoplasm. In considering the data of Table I, it is evident that some variation is present, even when the values are calculated on a fat-free basis. Sources of variation include losses of electrolyte when tissue specimens are ashed, technical difficulties in analyzing T HE EARLY NINETEENTH CENTURY wit