Hi,
Thanks for all the replies. His back pain appears to be right at the base of his spine. At least that is where he is always showing me when he talks about his back hurting.
It may be that his body is getting used to carrying the weight differently. It seems like his back started hurting around the 30 lb weight loss mark and hasn't gotten any better. If he stands for long periods of time he is in pain.
I've told him he needs to go to the Doctor, but of course, being a man he has that "I'm ok, I don't need to go to the doctor syndrome".
Thanks for all of the suggestions.