If your father suddenly lost his appetite, it is time to bring him to see a doctor to rule out some serious health conditions or medication side effects. Some illnesses can cause changes in taste and appetite, for example: dementia such as Alzheimer's, stroke, Parkinson's disease, chronic heart failure, chronic renal failure, etc. Some medication side effects such as dry mouth or a metallic, bitter or salty taste may cause a loss of appetite. Also, any acute infection can impair appetite. If loss of appetite is not caused by medication side effects or health conditions, then there are other reasons why your father could not want to eat:
1) Living and eating alone can cause reduced appetite. Elderly who live alone might not be eating because preparing meals has become too difficult.
2) Difficulty chewing due to dental problems, dry mouth, gum problems, toothache, etc.
3) As a person ages, they can lose a significant number of taste buds and normal food might be unappetizing for them.
4) Regular exercise and activity helps boost appetite.
5) Depression is known to impair appetite and is common in older people with reported rates of 9% in community dwelling older people.
Depression affects one in ten people over 65 years and it should be treated. What are the common symptoms of depression in older people?
-Sleeping problems, insomnia or oversleeping
-Loss of appetite
-Aches or pains, headaches
Depression is not a part of normal aging! Certain medications and some medical conditions can cause the same symptoms as depression. If your father does not have any acute or exacerbation of chronic medical conditions, he should be evaluated for possible depression.
He/she will try to look at your father holistically by taking into account other medical conditions, what medications your father is on, and how much your father can do for himself.
I hope this helps.