The Post-Gazette reports that the Pirates are unhappy with Pedro Alvarez's weight and strength, and based solely on the picture the Post-Gazette has provided (which, to be fair, is just one picture, and we all have pictures that are unflattering and unrepresentative), I can see why--he looks fat.
I suspect this is just a blip on the radar, and it's probably nothing to worry about in the grand scheme of things, but Alvarez is the most valuable asset in the entire organization, so the details of these next couple of years have the potential to matter a great deal.