Some of my cats would also be very large by now if I hadn't stopped free feeding. I now feed them 4 small meals a day and it seems to be working. I'm feeding all of them Innova Evo which is a very high protein grain free food. It also has a lot of calories so they don't need to eat much of it. They probably only eat about 1/2 cup or a bit less per day and one 15.4oz bag will last me about 1 month which isn't too bad considering that I have 6 cats. I also give them some of the Innova Evo wet food and some of Evanger's Organic Butternut Squash and Turkey Dinner wet food which are also grain free.

I hope that your cat will be able to start losing weight. You might also want to consider having his thyroid tested. I think that most bags of cat food also have a feeding amount for cats that are overweight so you should try to follow this. You don't want him to loose the weight too quickly though because this could cause some health problems. You might also want to buy a laser pointer to play with him. Most cats love these and will run and chase after them. Good luck.