Largest & smallest in terms of what? weight? Should hardly matter in chess - after all chess is about brains and not size.
Does size matter?

what is interesting is that most of the world champions that i see in pics are quite thin and i find it interesting that would be the case.
Well, for one, Garry Kasparov was an avid soccer player....I'd say that most elite players are in very good shape.
People generally perform their best when in good health. But of course, there is an answer for anything on google :)

Studies have linked physical activity to mental ability; though this hardly disqualifies a person from being a top notch chess player if they're not in shape.
Who was the largest world champion? Who is the biggest current grandmaster? Smallest?