The weight of the body is also related to the action of the thyroid gland, which has a part in determining the basal metabolism. Fever will increase the metabolic rate. Excess action of the thyroid will also give a rate over on the plus side whereas deficient action of the thyroid moves the rate to the minus side.
Eating is regulated by many factors. Appetite may be part of a habit of large eating. Many families put overemphasis on eating. Grandmothers offer food as cures for most family disturbances. Sometimes a person who has had an active life with heavy eating changes to a sedentary life. The eating habits persist and he puts on weight. Some people eat as a substitute for satisfactions that they do not obtain through other emotional sources. Incidentally, alcoholics frequently drink because they escape other demands in this way. An unusual cause of excessive eating is overactivity of the pancreas gland in developing insulin. An injury to the brain which affects certain portions of a part of the brain called the hypothalamus may be associated with the development of a voracious appetite. But by far the vast majority of cases of obesity are due to taking too much food in relation to the metabolism and activity of the body.
Loss of weight can be produced by lowering the calorie intake to less than the body requirement. Starvation may result from lack of appetite, which is called “anorexia.” Loss of appetite occurs in acute and chronic infections, in certain forms of cancer and glandular diseases. Loss of appetite may be wholly psychologic or mental, producing a condition called anorexia nervosa.