Sorry to Jasmine for calling her a "he"! She is too cute laying there like that.
My cats rarely ever lay on their backs. Unless they are trying to lure someone into petting them and then springing the trap.
Pete has been seen by the vet. He said to limit his food, too, but he just doesn't do it very often. I have 4 cats inside and I am liable to have a revolt if I start limiting the food supply.
Snow only comes by and eats a couple of bites at a time two or three times a day. And if the dish is empty he will wake you up, no matter what time it is. And he doesn't take no for an answer.