Sabathia has been a workhorse for many,many years. He's thrown a ridiculous number of innings over his professional career. http://www.fangraphs.com/statss.aspx?playerid=404&position=P
IMHO this health question/issue has come up because of a lack of "Ws", and team wins. The Yankees are in a slight decline right now, and Sabathia is right in the middle of it. The Yankees defense is incredibly suspect in terms of range and skill. If Sabathia had 20 wins last year, there would have been an article about how MLB pitchers are too skinny.
Sabathia is what he is....a big man. Only he and his trainers know where he needs to be optimally for health and results. The Yankees could help him out by giving him a reliable and more consistent catcher, and a younger, more mobile defense. IMHO Sabathia is not the problem, but part of the solution.