I currently feed all of my cats Innova Evo which is a very high protein grain free food. I don't free feed them any more so I give them 4 small feedings a day. Each cat eats about 1/2 cup of dry food per day and Storm and Sunny also eat some of the canned food too. I use the 95% Chicken & Turkey canned food. Since this food doesn't have any grains and is very high in protein 5 of my cats did lose weight. They don't have to eat as much because of the high protein and high calorie's that this food has. Starr is on prednisolone so this is why he's still on the heavy side.

I know that your cats shouldn't lose weight too quickly or else this could cause health problems. You may want to ask your vet about the amount of weight that they should lose and how quickly to go about doing it. Here's a link the tells how much to feed a cat: http://www.askthecatdoctor.com/howmuchtofeedcat.html.

This is what part of it says:
Oh, and PLEASE follow this rule. Do not let your cat lose more than 1/2 pound per month. If a cat loses weight too quickly, he is in danger of developing hepatic lipidosis (fatty liver syndrome) and trust me, you absolutely don't want that to happen!

So, again, no more than 1/2 pound of weight loss per month. Even if your cat needs to lose 10 pounds,(look at the picture below if you don't think that's possible!) don't let him lose more than 6 pounds per year.

Good luck.