From my reading I understand the vitamins and lemon juice will be counter productive to the reason to water fast. You may even loose muscle mass by taking in anything other than pure water which as a bodybuilder you will not want. If you have ample body fat and have been on a vitamin for awhile your supplies will be fine to maintain a healthy fast for healing and detox, the weight loss is just a bonus, not the reason to water fast. Have you thought about other routes such as raw diets or juice fasting which isn't as harsh, still will detox you to get the weight off? Water Fasting is honestly for deeper issues than just weight loss. Now if you go into it as the beginning of a lifestyle change and truely change the diet post fast (not eat anything and everything ;-) ) then it's a great tool. Good luck!