While the term outside of the scientific literature is often used interchangeably with anorexia nervosa, many possible causes exist for a loss of appetite, some of which may be harmless, while others indicate a serious clinical condition or pose a significant risk.

Appetite is thought to be stimulated by interplay between peripheral signals to the brain (taste, smell, sight, gut hormones) as well as the balance of neurotransmitters and neuropeptides in the hypothalamus.

[8] Examples of these signals or hormones include neuropeptide Y, leptin, ghrelin, insulin, serotonin, and orexins (also called hypocretins).

[19] Care must be taken when a patient begins to eat after prolonged starvation to avoid the potentially fatal complications of refeeding syndrome.

Thus, the reinitiation of food or oral intake is usually started slowly and requires close observation under supervision by trained healthcare professionals.