Its not water weight thats lost. Most people on the fat-fast are eating salted peanuts. The weight comes right back on because of set-point. If you gain it back, you didn't break the plateau. Is it water? sort of. When fat is lost, water is retained. What your gaining back though, is fat. Your metabolism crashes when you plateau, fat-fasting increases ketosis. Weight falls off you. But your metabolism will not jump up again until the entire range is broken. That can be as many as 10lbs one may have to lose to clear the range. If you don't have the will-power to do a fat-fast 4 days, or 4 days on 4 days off and 4 on... as a worse case scenerio... then do a 3 or 4 hours of walking everyday on the tredmill for a week. Plateaus are broken with speed, not consistency.