Anorexia (deriving from the Greek word ανορεξία = without appetite (αν = without + όρεξη = appetite)) is the medical name for loss of appetite. In particular, anorexia nervosa is an eating disorder characterised by voluntary starvation and exercise stress.

Anorexia is also symptomatic of a number of diseases including cat scratch fever, atypical pneumonia, syphilis, appendicitis, and the end stages of Alzheimer's disease. Anorexia is a symptom of drug addiction to Methamphetamine, for example, and a side effect of many medical drugs.

Anorexia may also be an indicator of radiation poisoning.

Anorexia is a disease. A person who is anorexic is likely to be infertile due to low body fat. Anorexia hurts a person's immune system because without proper nutrition an anorexic person is more susceptible to any number of sicknesses and viruses. Anorexia causes the body to almost go into a state of hibernation, conserving fats and vitamins as much as possible. Because of this hibernation-like state, anorexic body's will produce more body hair to keep the body temperature stable, something a normal body would do on its own. Anorexia also causes brittle bones. Many people die with anorexia due to any number of complications. Many females who become anorexic are looking to fit a certain modelesque appearance, but the truth is that the female body type for models is changing to a muscular, healthy female.