I think I remember reading somewhere that diet coke actually contains more glucose than regular coke, it just has less sugar in general. Not entirely sure if that's correct but I think it is The glucose is the stuff that makes you pile on the pounds, when it isn't needed, it's stored in the body as starch. The more you drink, the more starch builds up in the fat reserves. It can be broken down but the more starch you have the longer it takes. Try drinking mineral water or orange juice when you want a coke, you feel so much more clear-headed and refreshed after having a drink like that