Catabolic wasting (cachexia) is a clinical wasting syndrome characterized by unintended and progressive weight loss, weakness, low body fat and muscle. At least 5% of body weight is lost. Cachexia is not caused by poor appetite and nutritional intake, but rather a metabolic state in which a "breaking down" rather than "building up" occurs in bodily tissues, no matter how much nutritional intake occurs. Additionally, whether a patient receives oral or intravenous nutrition makes no difference. The patient simply cannot gain weight, so eating more is not a solution.
It is estimated that half of all cancer patients experience catabolic wasting, with a higher occurrence seen in cases of malignancies of the lung, pancreas, and gastrointestinal tract. The syndrome is equally common in AIDS patients and can also be present in bacterial and parasitic diseases, rheumatoid arthritis, and chronic diseases of the bowel, liver, lungs, and heart. It is usually associated with anorexia (i.e., loss of appetite) and can manifest as a condition in aging or as a result of physical trauma. Catabolic wasting diminishes quality of life, worsens the underlying condition, and is a major cause of death.