My 16 Year Old Son Is Trying To Cut Weight

My 16 year old son is trying to cut weight for wrestling Regionals. He's looking to lose 5-7 lbs. in two weeks. That's a lot in a short amount of time in my mind. Aside from starving himself or becoming dehydrated, is a (1 week) whole body cleanse a safe way to shed "sludge" to help in minor weight loss? Or is a there a optimal caloric intake to assist in this as an alternative? He's an extremely conditioned, multi-sport athlete (6' 1", 178 lbs). I don't want to sound like a crazy mom, but I'm surprised by what some boys do to cut weight and want to help my son make a better choice to help him reach his goal. Thank you.