I'm not a food faddist but I've tried the Hay Diet a couple of times and it really works at keeping you regular, sleeping well at night and staying alert all day.
One of the things I learned from Hay is that to digest carbs properly they need to be eaten slowly and very well chewed. So my office lunch, when I'm in that phase, is a mixed salad with tons of flavour in it (sliced onions, basil, a tasty dressing) with a couple of slices of good quality wholemeal bread to go with, consumed at leisure.