When we see weight loss with an apparently normal or increased appetite we need to worry about disease processes that either don't allow him to digest and/or absorb the food
he is taking (such as diabetes
, liver disease, primary intestinal or pancreatic disease including cancers) or those that lead to a higher metabolic rate such as hyperthyroidism
or cancer. Although parasites can cause loose stools they rarely cause actual weight loss in an otherwise healthy adult cat.In an older cat the more common diseases we see include hyperthyroidism (a tumor of the thyroid gland that overproduces thyroid hormones) or if he were drinking more and urinating a tremendous amount, diabetes. Sometimes early on with diabetes we only see weight loss.Both diabetes and hyperthyroidism are treatable or at least manageable. Hyperthyroidism is controlled with daily oral medication (Tapazole, also called methimazole) or a very special diet called y/d which is very low in iodine so he can't make thyroid hormone. Both of these must be done for the rest of his life or treatment with radioactive iodine to selectively kill tumor cells which is usually a one time therapy. There are pros and cons to each therapy which your veterinarian can discuss with you after getting a firm diagnosis. In Bot's case because you cannot control what else he eats diet is NOT a good option because he can eat whatever he likes along with the special diet, defeating the purpose of the diet (limiting iodine).Hyperthyroidism is not painful, but elevated thyroid hormones can make them feel edgy or nervous and thus cranky, increase the heart rate and interfere with sleep, like drinking way too much coffee or energy drinks. Some cats will overgroom becuase they feel anxious but rarely to a significant degree.Long term if left untreated hyperthyroidism can lead to heart disease, hypertension, possible eye damage as well as kidney
and liver damage. But if caught and treated many of these things can be reversed.Diabetes is controlled with diet and insulin therapy. Has he had any testing done to achieve a diagnosis? Ideally he should have a complete blood count and biochemistry profile with T-4 checked as well as a urinalysis. These tests often give us the information that we need.If those aren't diagnostic then it is time to move on to more specialized testing. I recommend checking vitamin B levels to look for signs of intestinal disease, a test for pancreatic insufficiency called a TLI, and an abdominal ultrasound to look for signs of changes in the walls of the intestines as well as evaluating his organs. He may need an endoscopy to collect biopsies of his intestines if they look abnormal.If he has any evidence of dental disease then he may need some radiographs of his mouth and tooth roots, although dental disease alone rarely leads to weight loss, especially in a cat that is eating well. In the meantime you might try feeding him a higher calorie prescription food called Hills a/d or Iams Maximum Calorie from your veterinarian and make sure he has access to plenty of fresh, clean water. Fur loss in an outdoor cat is almost always due to parasites of some type, the most common one being fleas. Cats that are allergic scratch excessively. I'd apply topical flea protection every 28 days. Both Advantage II and Frontline Plus work quite well at killing fleas and are less likely to create a skin reaction than the over the counter pet store products.Other possible causes include ear
mites, sarcoptic or demodex mites or ringworm
(fungal infection) and those your veterinarian can check him for if you can catch him and have him examined. Best of luck with Bot, please let me know if you have any further questions.