I have a 3 year old overweight cat (Stitch), and a 7 month old kitten (Sully). I've kept Stitch on a grain free food for over a year now, because I feel like it's better for her, and when she has grain, she has THE MOST heinous stinky poop ever. She was eating Blue Buffalo Wilderness, and switching between the types of meat from time to time. But she was becoming less and less active, and gaining more and more weight. I would put about a cup a day in her bowl, and she just picks at it throughout the day.
Sully came to me eating ProPlan, but I figured it would be easier to switch them both to the same food, as he seemed to prefer Stitch's food to his own anyways.
I thought that I would have to switch Stitch to a regular indoor cat food to help her lose weight, but that would mean putting her back on grain. Then I discovered that Wilderness came out with a Weight Control food. She seems to have lost a little bit of weight (i'm just going by her appearance), which I think is a combination of the food and being chased around the house by a new kitten. My only concern is Sully. Since he insists on eating her food too, I also feed him the Weight Control. Is it safe for him to be eating that? I fill both their bowls at night once a day (so they let me sleep), and usually by 4 or 5 the next day, they're empty. I just don't want to worry about stunting his development or something. They're both used to free feeding, so they won't eat an entire bowl if I put it down.