Anorexia is a medical term for aloss ofappetite. While the term outside of the scientific literature is often used interchangeably withanorexia 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.
The symptom also occurs in non-human animals, such as cats,[1][2] dogs,[3][4] cattle, goats, and sheep.[5] In these species, anorexia may be referred to asinappetence. As in humans, loss of appetite can be due to a range of diseases and conditions, as well as environmental and psychological factors.[2][4]
Anorexia simply manifests as a decreased or loss of appetite. This canpresent as not feeling hungry or lacking the desire to eat.[7] Sometimes people do not even notice they lack an appetite until they begin to lose weight from eating less. In other cases, it can be more noticeable, such as when a person becomes nauseated from just the thought of eating. Any form of decreased appetite that leads to changes in the body (such as weight loss or muscle loss) and is not done intentionally as part of dieting is clinically significant.[8]
Appetite stimulation and suppression is a complex process involving many different parts of the brain and body by the use of various hormones and signals. Appetite is thought to be stimulated by interplay between peripheral signals to the brain (taste, smell, sight, gut hormones) as well as the balance ofneurotransmitters andneuropeptides in thehypothalamus.[8] Examples of these signals or hormones includeneuropeptide Y,leptin,ghrelin,insulin,serotonin, andorexins (also called hypocretins). Anything that causes an imbalance of these signals or hormones can lead to the symptom of anorexia. While it is known that these signals and hormones help control appetite, the complicated mechanisms regarding a pathological increase or decrease in appetite are still being explored.[8]
Other drugs may be used to intentionally cause anorexia in order to help a patientpreoperative fasting prior togeneral anesthesia. It is important to avoid food before surgery to mitigate the risk ofpulmonary aspiration, which can be fatal.
During the post-operative recovery period for atonsillectomy oradenoidectomy, it is common for adult patients to experience a lack of appetite until their throat significantly heals (usually 10–14 days).[17]
Anorexia is a relatively common condition that can lead patients to have dangerous electrolyte imbalances, leading to acquiredlong QT syndrome which can result insudden cardiac death. This can develop over a prolonged period of time, and the risk is further heightened when feeding resumes after a period of abstaining from consumption.[18]
Care must be taken when a patient begins to eat after prolonged starvation to avoid the potentially fatal complications ofrefeeding syndrome. The initial signs of refeeding syndrome are minimal, but can rapidly progress to death. Thus, the reinitiation of food or oral intake is usually started slowly and requires close observation under supervision by trained healthcare professionals. This is usually done in a hospital or nutritional rehabilitation center.[18]
^abLlera, Ryan; Downing, Robin."Anorexia in Dogs".VCA Animal Hospital.Archived from the original on July 19, 2020. RetrievedJuly 19, 2020.
^Jubb, Tristan; Perkins, Nigel."Inappetence/Inanition".Veterinary Handbook for the Livestock Export Industry. Australian Livestock Export Corporation, Meat & Livestock Australia.Archived from the original on July 19, 2020. RetrievedJuly 19, 2020.
^Murray, M. J.; Murray, A. B. (1979). "Anorexia of infection as a mechanism of host defense".The American Journal of Clinical Nutrition.32 (3):593–596.doi:10.1093/ajcn/32.3.593.PMID283688.
