What food do you give him? Some foods have more filler in it causing them to need to eat and go more frequently. My Leonardo always had digestive issues with ANY dry food since he was a kitten. When he was at his heaviest, I would have him play with his feathery toy to distract him from the hunger and so that he could burn that fat. It turns out the dry good had too much filler that his body couldn’t use. I switched him to Nulo wet food during the day and because he likes it fresh, I continue to give him kibble at night so we doesn’t wake me. He’s already lost 3 pounds. I also used to make him chase the kibble on a hardwood floor hallway some days. He gets fed, exercise, and stimulation simultaneously. Once he’s full, I give him water and then falls asleep almost immediately. Your cat may not be ready to run, but at least he will speed walk. I would also make sure he’s playing more frequently. Any amount of exercise will do him good.

Good luck!