this from sfgiants.com about renteria

"Moreover, according to his agents, he has shed more than 10 pounds this offseason to get himself fit."

i swear that every time i have heard this, or the opposite "adding ten pounds of muscle",  the player stinks instead of improving.

somewhere in the back of my head i remember a story that wilson is going to help zito add muscle this offseason...so does that mean he goes from terrible pitcher to some sort of  square root of negative one meets a bose-einstein condensate sort of pitcher?

i didnt mean to sound that douchebaggy with a random reference, but i said it and ill stick by it.

so i pose the question(s),  how much of a role does shedding or gaing weight in an offseason really have? anyone have any specific examples of players succeeding or failing after such changes?