1 - Body Composition in Health and Disease

Abstract

This chapter discusses the composition of the body in respect of water and electrolytes and the effects of disease on this. It also discusses the concept of body spaces and principles of measurement. The most common technique uses radio-isotopes or certain substances that are distributed virtually entirely within the body space concerned. Another technique is by whole body counting that can measure the naturally occurring radioactive isotopes in the body. The red cell volume and plasma volume can be measured separately or the plasma volume is measured and allowance is made for the hematocrit. The chapter also discusses body ionic masses. It additionally discusses the control of body composition. The composition of the body is not static but varies with body development and as a result of stress in the form of disease and trauma. The chapter presents the compositions of body in abnormal state. In starvation associated for example with carcinoma of the esophagus, a process of cannibalism occurs where fat and protein is broken down slowly to provide energy for normal body metabolism. This leads to a decrease in intracellular water—as the cells decrease—and an increase in the extracellular water which ultimately can become so excessive that it is clinically apparent as starvation edema. Nitrogen is excreted in the urine—and as there is no intake—this represents the wasting of cells in the lean tissues.