I think it depends on the person. I drank lots of diet coke while on induction and still lost lots of weight. I eventually switched to caffeine free , then sodium free diet cola. The caffeine didn't make any difference, but I think the sodium does. I do sleep a lot better without the caffeine though! I still drink a lot (2 liters a day) of caffeine free, sodium free diet cola and hardly any water. It works for me! It's just not something I'm willing to give up!