With respect to food, the normal domestic cat problem is overeating or perhaps overfeeding. However, it can be the opposite.
One reason for a cat being hungry might be, albeit unusually, that the guardian is under feeding her cat resulting in the cat being perpetually hungry. The person might have a distorted view of what a normal feline diet should be and projects this onto their cat’s feeding regime.
There is the obvious reason that your cat might be highly active, far more active than is normal, because he explores the outside. This is an indoor/outdoor cat who may travel fairly long distances at night. This will make him hungry in the morning. The levels of hunger may surprise the owner but they will be normal.
Another possibility would be health-related namely that your cat has parasitic worms. It is said that worms in the gastro-intestinal tract take from the cat certain nutrients and therefore the cat is more likely to be hungry in order to replace those lost nutrients. However, the counterargument is that in an infestation of a gastro- intestinal parasite the cat’s health will decline, he’ll feel ill and lose his appetite followed by loss of weight, diarrhoea and anaemia. So, I’m not so sure that roundworms and other parasitic infestations of the gastric tract do in fact result in your cat being hungry.
Thyroid Cancer or Sugar Diabetes
There are two other diseases affecting cats which cause him or her to have an increased appetite namely hyperthyroidism and diabetes. Hyperthyroidism is nearly always thyroid cancer, often affecting older cats. The increase in thyroid hormone tends to cause an increase in appetite. Where once the cat was a finicky eater he now wolfs down everything that is given to him followed by an increase in activity.
Sugar diabetes develops in about 1 in 400 cats. It’s due to an inadequate production of insulin and in the early stages the cat will try to compensate for the inability to metabolise blood glucose by eating more. Therefore, the cat will demonstrate hunger. However, later on there is a drop in appetite due to the effects of malnourishment.
We read a lot about the failure of cat guardians to adequately stimulate their cats for various reasons one of which is because they are full-time indoor cats and the home is insufficiently enriched to provide a stimulating environment. Under the circumstances a cat might become bored and eat as a diversion. It is pleasurable and stimulating to eat. An associated issue might be over-grooming because this is also pleasurable and calming to a domestic cat. In bad cases of feline boredom, the cat might become depressed and this also may encourage overeating.
If the cat’s diet is inadequate in terms of food quality i.e. the food does not contain adequate nutrients then the cat might eat to compensate.
I also think by the way that sometimes dry cat food is somewhat addictive because of the high carbohydrate content which is required in order to manufacture dry kibble. This in itself can result in overeating. This is not technically being hungry but being hungry is the root cause of eating and it can cause overeating if that hunger is false.