I have a fifteen year old white cat. He is very skinny buts eat alot and still does not gain weight. Mostly moist because his teeth are not that good. i heard that is common in all white cats. I have to give him antirobe drops since I can't have his teeth removed because of his age and he has a heart murmer. I thought it could be a thyroid problem and took him to 3 different vets. None of them new what was wrong, one even said last January that he is a sick cat & I could have him put to sleep or bring him home to die. But she probably did not know he was always skinny. Anybody have any ideas or is it just old age. Thanks.