If's he's diabetic he's probably going to have to live with very minimal carbs (rice, pasta, potatoes, bread, anything with sugar). Those are all high on the Glycemic Index (except the stuff they make now specifically for diabetics. Those are usually in the pharmacy or the health food isles). He'll also have to watch his fruits (which are high in natural sugar). I'd consult his nutritionist to find out how many carbs a day he's "allowed".