I am IR, or prediabetic and so far have fended it off for 10 years.
Is he using a meter? Does he know his calorie bracket and his exchanges break out? Does he exercise regularly? (Exercise brings down insulin.)
Here's some starting menus/recipes to help get a handle on it.
http://diabeticgourmet.com/Food_and_...Meal_Planning/
This is good too:
http://www.amazon.com/Official-Pocke...5967549&sr=1-1
If he's ready to take the hardcore leap -- could even go vegan.
http://www.amazon.com/30-Day-Diabete.../dp/0399534210
When I was closer to vegan/vegetarian I got off the Metformin and doc told me my labs were "normal and you couldn't even tell I was IR."
If he's wanting to stick to non-vegetarian/flexitarian... the whole foods/eating clean approach might be better than vegan/vegetarian then. I'm at this stage again and will take the veg approach later. (I find flex easier when traveling).
HTH!
A.