|Diabetics can develop what is called diabetic neuropathy. There are treatments for it to reduce the pain and it can get better over time, with better blood sugar control.
However, I'm not sure if your husband's doctor is taking his condition very seriously if all he was told was to lose "a bit of weight" and change his diet. If he is actually full diabetic, he needs medication. Was he given any pills or insulin? If not, I would encourage him to get a second opinion from an Endocrinologist, not just a family doctor.
Best of luck to both of you.