It depends on the individual. Some guys fight better with a bit of flab. Fedor was a great example. Other guys fight better totally ripped, like say Sean Sherk. Some guys look like Cain and then drop fat and perform like shit. If you are in to fight sports, this wouldn't be any big question in your mind. It did used to make me wonder what was up with Chuck Liddell and his distended stomach....that was weird.