One of my cats — female, domestic longhair, 7 years old, healthy — won’t stop eating until the food is gone or she’s sick. She usually finishes eating first, and then tries to take food from the others, and if they leave any and I’m not quick enough to catch her, she’ll finish theirs, too. I’ve had her, her brother and their mother since the kittens were 5 weeks old. Their mother is a “healthy” eater, too, but the brother and mother are nothing compared to my girl. Any ideas why she eats so much?
A good appetite on a cat usually indicates that the cat is healthy, however, an increased or ravenous appetite can be a sign of illness in some cats. Diabetes and hyperthyroidism are two common illnesses that cause increased appetite in cats. Diabetes causes cats to drink excessively, urinate excessively, and lose weight.
Hyperthyroidism is a glandular disorder in which the thyroid gland in the neck produces an excessive amount of thyroid hormone. This is usually seen in older cats — average age being around 13 or 14 — however, occasionally it can be seen in middle-aged cats.
I recommend that you have your veterinarian run some basic blood tests to make sure there isn’t a metabolic disorder that might explain your cat’s exceptionally good appetite.
Maldigestion would be another possible cause for your cat’s ravenous appetite. There is an uncommon condition in cats called Exocrine Pancreatic Insufficiency (EPI) in which the pancreas does not produce enough enzymes necessary to properly digest food. Cats eat, but the undigested nutrients do not get absorbed by the body, and the cat eats excessively because she feels as if she is starving. Affected cats often have diarrhea and weight loss.
Diagnosis is easily achieved by running a blood test called a Trypsin-Like Immunoreactivity (TLI) test. Although you mention that your cat is healthy, I think it would be a good idea to run these tests just to rule out any serious medical cause for your cat’s overactive appetite.