I have done this diet now for quite awhile (this article was written a few years ago but gets a new date whenever edited). I will tell you that to start with, I drank the diet soda with the caffeine and chewed gum during my fasting period. I lost significant amounts of weight. Now, I'm very adjusted to this lifestyle and I drink only water and I fast closer to 20 hours a day. I think when people are beginning to fast, they should do what they need to do to make it work as long as it's not hindering their progress. As their bodies become more adept at going without food, most people will find their bodies feel best without these things during the fasting period and will naturally start to move away from them.