After doing a bit of searching, I found this piece about his weight. He had to gain weight for his role in the movie We Are Marshall.
On preparing for his We Are Marshall role:
"When I did this movie, I was 16 lbs. heavier than I am now. I had a big caboose and a big belly."
That explains the belly pics and that's one of the reasons he was so tight with Armstrong as well, losing the extra weight.