my cat

Have you had her checked for worms? Rather than guessing, I\\\’d advise you to see your vet for a real diagnosis. Call ahead. Your vet will need a stool sample to search for worm eggs.

It could be tape worms. Tape worms are caused by fleas and a cat will be unable to gain weight. If you see what appears to be a grain of rice on your cat\\\’s butt….then she has tapeworm. It\\\’s imperative that you get your cat treated asap. Flea bite anemia occurs in severe flea infestations or in tiny kittens. When a flea bites, it feeds on blood. With many fleas feeding at the same time, significant blood loss can occur, resulting in severe anemia. Blood transfusions, iron supplementation and hospitalization are frequently necessary. Some cats may not survive flea bite anemia.

I would follow catsofmany\\\’s advice. if it is not worms, bring along an ingredients list from your cat\\\’s food and ask the vet if the food is any good. If it is mostly grain filler, there may be little nutritional value in it.

As stated before you need to get your cat to a vet and bring in a fecal sample, the vet will likely find a parasite which is totally treatable. If your cat does not have a parasite it could be more serious. Waiting to take her in will not help, it can only make the problem more serious.
best of luck to you and your kittie

Have your vet check her for hyper-active thyroid. Cats love to eat and do not gain weight. This is a serious illness that leads to kidney problems. Take her to the vet…..

my kittens were the same they they ate like pigs and werent gainging any weight i went to go and clean their litter box and i seen little white worms in their poop i went out and bought them some dewormer from a pet store and they have gained weight because their worms are gone now, take them to the vet or call your vet thats what i did and if they cant tell you anything over the phone then i would take them to a vet just to be sure

well………… she may eat alot but there might not be a lot of calaries in the food she eats

Source Link: change food

what you need to do is feed the cat and dont let it excercise too too much you want it to gain some weight so it can be strong and healthy and an overall good cat because you dont want the neighbors to feel as though your malnourishing your cat. feed it 17 cans of tuna a day and some mixed in wet food and dont allow too much excercise