I've tried to do Water Fasting in the past and never got beyond about two days and felt horrible and hungry the whole time. With the Master Cleanse, you are not starving yourself. You still get all the necessary nutrients your body needs for health from the lemons and the maple syrup, and the cayenne gives other benefits (loosening mucus, warming you, and I don't know what else). It's easier to lose weight when you are not starving, to keep your metabolism up.