Most cats react the same way we humans do to corn these days. It makes them fat! I am not kidding you. If your cat is overweight even when you are not over feeding, take a look at the food you are feeding him/her and if corn is in the mix, that is more than likely the reason. A lot of cats have minor or major allergies to corn as well, many only showing slight symptoms until one day their health takes a turn for the worse. Corn is one thing you want to avoid.