This whole "DDP Yoga" shit is unfounded. It was never confirmed that he was ever on DDP Yoga. All we ever got was that DDP said that he heard Y2J was trying to convince Kane to get on the program. Nothing more.
And what do you mean where did his abs go? He had them for months, and still could. He's totally covered now.
However, Kane has a long history of getting in and out of great shape over the past few years, depending on his motivation. During Team Hell No, he was in great shape, during his 2010 World Title run, he was in GREAT shape, and he was slated to get into a feud with Punk, so he got in great shape. Plus, he had time off to film SNE2. Time off helps a lot.
The idea that anyone in WWE is on steroids now is silly. No one is that ridiculously huge anymore. The only person I would have suspected was Rock, but he's got all the tools to get big naturally. GGG isn't crazy enough to start doing anabolic steroids at the end of his career at the age of 47. The man has incredible genes. Both his parents are in their 90's and functioning well.