There is a big difference between cutting weight and becoming healthier. If he truly has weight to give, a healthy diet and exercise is appropriate whether he wrestles next year or not. Use wrestling as a motivation to get in better shape during the off season. It doesn't have to be miserable. A few small changes over a long period of time can make a big difference. You may find that a different mindset is a good thing for the whole family.

I would strongly encourage you to not quit wrestling for a reason like this.