Section I. BODY FLUIDS
The human body can continue to function much longer without food than without
water. Although a person deprived of food for extended periods may experience hunger
pangs (and even undergo personality changes), his body will continue to function well
enough to permit some use of all faculties. After a time, even this limited use will fade,
but this may take weeks or months. The lack of water can cause death within days or
even hours (in some cases). The reasons for this situation will be shown in Lesson 2.
All animals require a water environment. In the case of marine animals, the water
surrounds them. In the case of land animals, the water is carried within the body.
Homo sapiens (human beings) are no exception. Water supports life. The lack of water
destroys life. The percentages and fractions listed in this lesson may vary, depending
on the reference that you consult. This is caused by the different methods of
measurement used by the research laboratories. The variations from one reference to
another are slight and do not affect the general concept.
NORMAL FLUID CONTENT IN THE BODY
The average 70 kilogram (or 154 pound) adult male's body weight is
approximately 60 to 70 percent water (see figure 2-1). The more a person weighs (not
including body fat), the more water his body contains. The more fat is present in the
body, the less will be the total water content per unit of body weight. Fat has almost no
water, so fat people have lower water content per pound of body weight than slender
people. Water may account for 50 percent or less of their body weight. A newborn
infant may have 80 percent of total body weight in water. This proportion decreases
gradually as the child grows older and fat is added to the body.
Figure 2-1. Body water by body weight.