Molina is a catcher... OK, you knew that. Molina is in the highest level of baseball b/c of his catching. Hitting, running... not why he plays in MLB. He is a very good catcher. Fielding, game calling, base steals, etc.
Perhaps he is smart enough to realize the the knees (legs period) are crucial to continue being a MLB catcher. He is not getting any younger and less weight is key to keeping strong legs/knees for a long season. I doubt Molina will stick around late in his career as a DH/1B/PH type of guy. He knows as he turns 31 this summer, that it gets tougher doing the job that keeps him in MLB.
The anti Corky Miller approach.