Show him small ways that he can get into exercising and eating right. Don't over whelm him, and make it a subtle change. Suggest a 10min walk, make something different for dinner, a bit more healthier. Sometimes people complain but don't want to do it because they think they have to change their entire lives all at once. That's not the case, slowly changing and introducing things is just as, if not more, effective.
Like Mal said, if you can show him that he doesn't have to give everything up, than he might be more apt to do things.
OR, ask him how he'd like to change. Make a list. Would he be willing to take, three 10min walks a day? How about trading a highfat meal for a low fat one 4 times a week? Ask him what he's willing to change right off the bat, do that for a bit, then start in on different things.