Hello Dan....Good question (very good, as a matter of fact). As with "proper training", "proper nutrition" is a valuable part of the of the big picture. There are formulas that are used to determine specific ratios of macronutrients with relation to an individual's lean muscle mass to body fat percentage. It involves finding out your approx. caloric expenditure, determining an amount of calories that either needs to be added or subtracted from your intake to get the desired results. From what I understood of your post, you are looking at adding muscle to your frame (correct me if I am incorrect). Generally speaking (and that is because there are many factors), you would "tweak" added amounts of protein (used for repair and building muscle) while concentrating on required amounts of carbohydrates and fats for the task at hand. A good trainer has these tools. Also, the amount of weight you lift, the number of repetions you do and the number of sets in your routine needs to be determined. Gets kind of involved, huh?
I'll try to dig up a link that will at least get you on track. I'll send it to your email. Just keep in mind that any "diet" that severely restricts, or eliminates either protein, carbohydrate or fats...needs to be looked at closely. Nutrition is a "lifestyle", not a quick fix.
Dave