It makes me think it may be Martin Bormann, who was heavyset in build and looked a lot like that photo, I think. Bormann became Hitler's total right-hand man by the end of the '30s through the end of the war, and was constantly around Hitler. He became the gate-keeper for virtually all access to Hitler, I believe.
Here is another photo, with Bormann just to the right of Hitler (stage left). Hard to compare since it's not the same profile angle, but I think it may be the same man???
