Okay I have a fat cat (his name is Jack) and could perhaps be a record holder. He has to be around 40 pounds - no joke.
Now don't get me wrong he is a big cat, without the extra weight. I have a dog and another "regular" cat. Problem is that you can't really restrict food from Jack. He will eat the dogs food when we aren't looking, plus eat all the cat food. I feel like he would have to be in a house with restricted access to food.