In my opinion, you don't undo all the good. I mean I suppose if you went on one fast and then years of horrible eating habits..you probably would. I have been off an 18 day fast for about a month and a half and I have been eating not so good, HOWEVER, my body continues to work more efficently....I have only gained back 5 pounds when I should have gained it all, and my candida is not near as bad as it was. Would I still hold these benefits..a year from now? I don't know.