I drink water and pepsi max (better than diet, only 0.3. calories per can) I think the main reason for drinking so much is to help fill you up but i also thought that if you don't drink enough on a diet then it can hinder weight loss through water retention? I lost 6lbs on SF in a week a few weeks back through lots of exercise but the following week I stayed the same, I never drank much that week (headache on numerous occasions) and was told it was due to water retention ? Xxx