AGING IN WOMEN - THE 4-COMPARTMENT MODEL OF BODY-COMPOSITION

The four-compartment model of body composition was examined in 155 whi te women through measurement of total body carbon (TBC), nitrogen (TEN ), calcium (TBCa), and water levels. The age (mean +/- SD) of the popu lation was 51.4 +/- 13.5 years, and values for the four compartments w ere as follows (in kilograms): protein 8.9 +/- 1.0, water 30.9 +/- 3.5 , mineral 2.6 +/- 0.4, and fat 22.6 +/- 7.3. There was a linear change with age for protein and water, whereas mineral and fat were curvilin ear. These latter two compartments also showed differences in premenop ausal and postmenopausal rates of change. Various models were fit to t he data to adjust for body size and age. Each of the four compartments (mineral, water, fat, and protein) changed with age, with fat increas ing and the other compartments declining. The equation, y = age + age( 2) + height + weight, fit the data as well as the other models. Equati ons are provided to assess body composition in populations with disord ers of nutrition, as well as other illnesses, using height, weight, an d age as covariates. Since this was a cross sectional study, longitudi nal studies will have to be performed to confirm the accuracy of rates of change with age predicted with each compartment. Copyright (C) 199 6 by W.B. Saunders Company