It could be that he was not on a weight program when he first hit the tour. Many golfers were not on weight programs even just 10 years ago. In fact, my high school golf coach hated us lifting during season. The guy is bigger than he was 12 years ago, I would imagine most people on any decent program could do that. Besides, he is not a He-Man of any sort, he just looks to be in shape.
Hewas actuallylonger off the tee during his first few years on tour, and took a much more agressive swing at the ball.
Im not saying he is or he isnt, but there is not hardly enough evidence that would suggest he was taking anything.