Cachexia is a medical term meaning, approximately, "wasting." The sufferer loses muscle mass and bone density, depletes stores of fat, and becomes weak or tired. Cachexia occurs when a person is unable to keep food down, as in advanced cancer or some kinds of chemotherapy; when advanced disease processes have reduced the body's ability to regrow lost tissue, as in AIDS; or when a person refuses to take in adequate nutrition, as in anorexia nervosa.