A loss of appetite is termed ‘inappetence’. Inappetence refers to a lack of appetite, whereas anorexia refers to a complete lack of appetite, where a cat consistently refuses to eat and weight loss occurs.
There are many reasons why a cat may go off its food. Cats can be notoriously fussy eaters, and a change in their diet may lead to food avoidance. Therefore, always introduce a new diet to your cat in gradual stages, adding the new food as a small proportion of its existing diet and increasing this gradually.
However, a cat going off its food can indicate that it is feeling unwell. Most diseases depress a cat’s desire to eat; therefore, inappetence can be a sign that your cat is suffering from an illness.
If your cat is eating less than usual, or worse not at all, you should take it to see a vet as soon as possible. It is important to get the cause diagnosed and treatment started to minimise weight loss, which can lead to further health problems.
If no physical health issues causing inappetence can be identified, then the cause of appetite loss may be psychological. Inappetence can be caused by stress, in which case it is important to identify the cause of stress and eliminate it. There may be a trained member of the veterinary team at the clinic who can assess your cat’s environment and routine to identify any causes of stress, or seek the help of a trained behaviourist. See our advice page on choosing and using a cat behaviourist here: https://icatcare.org/advice/how-guides/how-choose-and-use-cat-behaviourist
In conclusion, it is important to take your cat to a vet for a health check if you notice a lack of appetite, to get to the root of the problem and for appropriate treatment.