Starvation in humans is an abnormal state, or syndrome, that results from a food intake of inadequate quantity or from a failure to properly metabolize food. In contrast most malnutrition is generally due to a poor diet, and together with many deficiency diseases results from poor quality diets deficient in particular nutrients (for example, iron deficiency leading to anemia). Starvation manifests itself first by weight loss and body wasting; if unrelieved, it may progress to emaciation, diarrhea that is difficult to treat, secondary infections, and eventually death by heart failure. Humans may die of cold in a few hours, or of thirst in a few days, but they usually die of hunger only after weeks of starvation.
Starvation may have several causes. Starvation among large groups of persons most commonly results from famine. Starvation in individuals may be secondary to certain diseases, most notably those which affect consumption, absorption, or proper metabolism of food and its nutrients. It may also result from food deprivation, such as during incarceration or when an abusive parent starves a child. Another form of starvation occurs in those who suffer from the disease anorexia nervosa or who for psychological reasons eat too little food.
Starvation leads first to the wasting away of the fat deposits of the body, both those beneath the skin and the deeper deposits. A normal human weighing 68 kg (150 lb) may have 16 kg (35 lb) of fat. After most of the fat reserves have been burned up, there may be progressive wasting of muscles and reduction in size of body organs, including the liver. The physiological response to starvation is to conserve energy by reducing activity. As starvation progresses, changes in the intestines lead to poor absorption of nutrients and diarrhea.
Blood pressure falls and the pulse slows. Eventually edema may occur. In women menstruation may cease, and in pregnant individuals spontaneous abortion or miscarriage may result. Life-threatening infections such as pneumonia and tuberculosis and micronutrient deficiencies commonly occur. In young children nutritional marasmus or kwashiorkor may develop.
The treatment of starvation depends on the severity of the condition. In moderate cases (loss of less than 20% of body weight) and where there is no diarrhea, any available and acceptable food is suitable for treatment. Intake of 4,000 or more calories per day with weight gains of 2 kg (4 lb) per week may occur. If the patient is enfeebled, and especially if diarrhea is severe, extreme caution is necessary in treatment. Injudicious feeding of unsuitable foods may result in death. Sometimes intravenous or intragastric (tube) feeding and the introduction of frequent small feedings of nutritious, easily digestible foods are needed until such time as the patient's digestive tract has had a chance to recover. In all cases appropriate treatment for any infectious disease needs to be a part of treatment. Vitamin and mineral supplements are often needed. If starvation is secondary to some other diseaseÑfor example, malabsorption, tuberculosis, cancer, or anorexia nervosaÑthen specific treatment appropriate for those conditions is needed.