Weight loss that is not easily explained is a significant symptom that needs to be investigated by a doctor. Diseases that increase metabolic rate (the rate at which the body’s basic functions work), a lack of nutrition, an increase in exercise, excessive sweating, an inability to absorb food (malabsorption), diarrhoea or any disease or inflammation that puts stress on the body can cause weight loss.
Any condition that causes persistent diarrhoea, nausea or vomiting will lead to weight loss. Sometimes, the diarrhoea and vomiting may be self induced in order to lose weight, or may be part of a number of different psychiatric conditions, including depression. Coeliac disease is an intolerance to wheat and other grains that causes fatigue, diarrhoea, flatulence and weight loss.
Anorexia nervosa is a psychiatric condition that normally occurs in young women who have a distorted image of their own body. They believe that they are fat when they are not, and so starve themselves in order to lose excessive amounts of weight. The patient can become seriously undernourished and emaciated, to the point of death, if adequate treatment is not available. Other symptoms include the cessation of menstrual periods, diffuse hair loss, an intolerance of cold, a slow pulse, irregular heartbeat and other complex hormonal disorders. Patients practice deceit to fool their family and doctors by appearing to eat normal meals but later vomit the food, use purgatives to clean out their bowel, or hide food during the meal.
Other common causes include any persistent infection (eg. tuberculosis, hepatitis, AIDS, brucellosis), autoimmune disorders (eg. rheumatoid arthritis, dermatomyositis, systemic lupus erythematosus), cancer of almost any organ, cirrhosis (damage to the liver), cholecystitis (inflammation or infection of the gall bladder), a peptic ulcer in the stomach and ulcerative colitis (lining of the large intestine ulcerates and bleeds).
Less common causes of weight loss include an overactive thyroid gland (hyperthyroidism), severe asthma, uncontrolled diabetes, parasites of the intestine, kidney failure, congestive cardiac failure, emphysema (incurable There are many rare conditions that may cause loss of weight including Crohn disease (inflammation of the small or large intestine), pancreatitis, tropical sprue (long term intestinal infection), Addison disease (underactive adrenal glands), diabetes insipidus and Letterer-Siwe syndrome.