Weight loss

This occurs any time there is a decrease in energy intake compared with energy expenditure. The decrease may be due to deliberate weight reduction or a change in diet or activity level. It may also be a symptom of a disorder. Unexplained weight loss should always be investigated by a doctor. Many diseases disrupt the appetite, which may lead to weight loss. Depression reduces the motivation to eat, peptic ulcer causes pain and possible food avoidance, and some kidney disorders cause loss of appetite due to the effect of uraemia. In anorexia nervosa and bulimia, complex psychological factors affect an individual’s eating pattern. Digestive disorders, such as gastroenteritis, lead to weight loss through vomiting. Cancer of the oesophagus (see oesophagus, cancer of) and stomach cancer cause loss of weight, as does malabsorption of nutrients in certain disorders of the intestine or pancreas. Some disorders cause weight loss by increasing the rate of metabolic activity in cells. Examples are any type of cancer, chronic infection such as tuberculosis, and hyperthyroidism. Untreated diabetes mellitus also causes weight loss due to a number of factors.