Some cats are great at eating only what they need, others gorge themselves on food until they're ready to throw up. My mom's cat is one of the former, that cat always has a bowl full of cat food that my mom periodically refills, but the cat never eats more than she needs. We on the other hand have three cats (yes, I know, that's one too many), one cat can self regulate, the second is kind of unknown, and the third one overeats like crazy, I think she just inhales the food without chewing. Since we feed them all at the same time, there is no way to portion control individual cats, so we just hold the fat one back for a couple of minutes to give the other two headstart. Since the fat one has less time to eat, that equates to smaller food portions. It took about 6 months of doing that to get measurable results, but now the fat one looks much better. She's still heavy, but a lot of it now is loose skin. It's also kind of a pain to hold her every time we feed the cats, but it's better than watch her slowly work her way to a stroke. So yes, it can be done. Portion control is the key. Start slowly reducing the portion size, and I mean slowly, and it will work itself out.