Not sure why I didn't post in this thread sooner!
Let me begin by saying that for once, I agree with you darius

Simba is most certainly
not fat in SP; he's just more mature, muscular and filled-out (there is a difference between filled-out and fat). I think those who bash Simba's looks in SP by saying he's fat are the same people who keep bashing SP for other reasons, and perhaps are looking for something more to support their allegation that SP was badly or crudely made, or just another reason to dislike it. Either way, I think they made him look the way he does in SP on purpose, and they did a good job of making him look older and more mature, but not fat. Remember, after all, that he wasn't
quiiiite an adult at the end of TLK.