Perhaps you are more concerned than you need to be. Neither your FBG nor your A1c are in the diabetic range. Yes, your BMI would indicate that you are overweight, but it sounds as though you are working on that with your exercise program. I have no idea whether the book to which you refer is a good one or not - I'm simply not familiar with it - but if you are concerned about diabetes, it certainly is a good idea to consider one's diet. Many people eat too many calories and too many carbohydrates and in particular, high glycemic carbohydrates.