Weight Clauses and Pro Athletes

We've addressed weight clauses before in player's contracts - including for Glen "Big Baby" Davis and Derek Caracter.  Jon Schuppe of NBC News now writes on the Phillies negotiating one with Delmon Young.

There's some reason to believe weight clauses are not especially effective -- the Bulls apparently tried weight clauses with Michael Sweetney, the now 30-year-old talented power forward who hasn't played in the NBA since 2007 due to obesity (the Celtics would later bring him to training camp but his weight had gotten too much).  Weight clauses might also prove counter-productive, given that some players play well heavy (David Wells, Charles Barkley etc.).

Then again, Davis slimmed down this season for the Orlando Magic and is having his best season in the NBA.  But hard it's to know if weight is the reason or if its because he's starting and is in the prime of his career at age 27.