Let me clear a few things up. When you dehydrate your body you are not losing weight, you are cutting weight. I promise you it will come back as soon as you start replenishing your fluids. Ultimate fighters and boxers alike will do this to their bodies about once every three months (sometimes less than once a year) on the professional level. Then, they will have up to 24 hours to recover. In that time they may actually gain back every bit of the 20 pounds they have cut, giving themselves what they perceive as a real advantage. Wrestlers do it once to twice a week. I would not suggest subjecting your body to that form of abuse.