Yeah that kind of extreme weight loss isn't good for you. I only ever dropped like 5 lbs max, just enough to make sure I'd hit my weight class but also stay near the top of it. For the really little kids there wasn't much difference in the weigh classes (like 105, 108, 115), but once you get up a little higher the difference between the classes starts getting wider (160, 171, 189, 215), so ideally you want to be right near the limit so you're not wrestling someone 15-20 lbs heavier than you...