We had a cat who was bulemic as a kitten, and scared of everything, and then obese as an adult and died too young. I wish I'd pampered him more because he was just so sweet but so scared ... but I was a new cat owner and didn't know what he needed.
Our two largest cats now are supposed to be large. They're truly huge. When they were about 4 they tipped the scales at 18 pounds, which the vet commented on, but which she said was perfectly fine for them.
But then they got up to 22 or 23 pounds and couldn't clean themselves well. They spent a few years at that weight before we took it seriously enough.
But now they're back down to 18 pounds. At age 12, 18 pounds is a little more flab than it was at age 4, and they still have a little bit of trouble getting to their nether regions, but it's a great improvement.
What did we do? We moved from wet food twice a day and dry food self feeding to:
wet food at most once a day - we have three cats in all and they split a 5.5 oz. They eat in separate rooms to make sure everyone gets as much as he wants from his own plate. The most aggressive eater is fed in the foyer where we can close the door.
Then small portions of the brands of dry food they most prefer - a couple of times a day.
And for overnight a little bit of a "healthy" brand which they don't like. So if they are really really really hungry, they'll eat it, but they won't eat it just for fun.
... and we did try to hug and play with them a little more than we had been.
p.s.
Some days they don't get wet food at all. Took a bit to stop them from begging for it everyday ... but now they're pretty good sports about their more limited diets.
Some days they do get a little extra treat. They love sliced deli meats ......