Do you measure out the food your fatty kitty is getting each day? If not then you should be.

Most foods have a feeding scale on the side of the bag. Find out what your kitty should weigh (call your vet if necessary) then feed your kitty according to that weight listed on your bag. Break that measured feeding up like 2-3 times a day. That way kitty won't be quite so hungry as when they are fed once a day.

Keeping cats separated during every feeding, or supervising the feeding will help make sure fatty kitty isn't getting more food than he's supposed to get.

Lots of play time, even if it's just laying there rolling around after a toy, will help some.