I am worried about my cat. getting too fat, a cat foot for wieght control?   

I am worried about my cat. HE is getting fatter just about every day. He has to have a scoop (A tesapoon) of wet cat food, and we feed him Deli-Cat, or Kit and Kaboodle for Dry Cat Food, and we also feed him Iams Weight control, but I don't think it's doing any good. I think he must weigh at least 15 #! What food should I feed him so he can lose weight. I had to buy another pet carrier because he can't fit in the one we got when we first got him, and sooner or later, he is not going to fit in the one I got last summer! Will he get fatter, should we put him on a diet? I would like to hear some opinions and ideas!.