Make vegetable soups for winter lunches at work. Most are superfree or if you use potato or parnsip it's at least free on green. Really warming and comforting (heat in the morning and put in a thermos at home if you've no microwave at work) and most importantly, filling!
You can even add pearl barley or pasta to bulk it out further, then have with a HexB choice - 5 scan bran, 4 ryvita or a couple of mini bread slices.