A careful medical examination always includes a record of the patient’s weight and, particularly, information as to whether he has been gaining or losing weight rapidly. Doctors have tabulations which show the average weight for people according to their age, sex, height, and body build. Some people are tall and thin with light bones and light muscles. Others may be stocky, short, muscular.
Water constitutes about seventy per cent of the body weight. About one fifth of all the water is outside the individual cells. This is found in the blood, the spinal fluid, the lymph and a small amount between the cells. The remainder of the body weight is in solid structures like the bones; most of the minerals of the body are in the bones. Sugars are stored in the body-principally in the liver and muscles-as glycogen.
Fat is an inactive material deposited around the body in storage depots.
Proteins are the chief building elements of the cells. The body needs four grams of water for each gram of protein. The amount of calories taken by the body to maintain its weight depends on the rate at which the body uses up material, and this in turn is related to the amount of activity. Growth requires increased calories. When inadequate amounts of calories are taken into the body the deficit is supplied by using up material from the tissues. The fat is drawn upon, but also the carbohydrates. When both fat and carbohydrate are utilized, the protein is taken up. This means the breakdown of some functioning cells.
Conditions in which there is interference with the usual elimination of sodium cause increased water retention and gain in weight. Examples are heart failure, toxemia of pregnancy, hardening or cirrhosis of the liver and congestive heart failure. Elimination of water is improved by stopping salt, improving heart action, or by drugs which increase the action of the kidneys.
Increase of fluid in the body occurs when the protein is inadequate.
In such cases restoration of protein results in elimination of water. Excess of sweating or severe diarrhea also draw water from the body and thus lower weight.