Studies on the Body Composition of the Old Persons

It is well recognized that the body composition varies with age. Since there is a constant potassium concentration in lean tissue, while fat contain little or no potassium, it might be possible to use body potassium concentration as an index of the body composition. Recently, the availability of the human whole body counter has openned a new area in the study of body potassium metabolism. In this study, the authors measured whole body potassium content, with the plastic scintillator type human counter, in 217 normal volunteers, namely 136 males, ranging in age from 6 to 82 years, and 81 females, from 6 to 80 years. In the old persons over 60 years of age, strict physical examinations were carried out in order to rule out subjects with latent illness. Skin-fold thickness was also measured in these old persons In both sexes, body potassium concentration decreased linearly after 40 years of age. In the subjects over 60 years of age, body potassium concentration showed highly significant negative correlations with the each value of skin-fold thickness of various parts of the body. In all of these old persons, the proportion of fat in the whole body calculated from the present potassium data according to the formula of G. B. Forbes, differed markedly from that calculated from skinfold thickness according to Nagamine's formula to be used in young adults. As one of the reasons of this discrepancy, the authors pointed out the infiltration of fat in the various organs and the increase of connective tissue which were usually found in the old persons.