The only thing different in my mans diet since being diagnosed w/diabetes are his pills. Why won't he comply?

He will not improve his diet. He eats what he wants when he wants. Because his sugar is pretty good, I think he thinks he doesn't need to change his lifestyle. I quit trying to help. Asking, helping, pleading, crying didn't do it , so I gave it all back to him and told him once he owned the disease than he could change. The fighting has ceased but that's about it. Help! HIs dad died from complications of diabetes.