How to approach?

[playfelt]

There are actually several genetic conditions where over eating and not understanding food needs is part of it. I wonder how often he visits the doctor. I would probably ask if he is being monitored for his food intake as you would like to speak with his nutritionist or could the parents pass on info they have been given regarding feeding frequency and amounts to serve. Doing it from the perspective of what you need will get you the info as to whether they have sought out this info and if not might put the thought in their heads that things are getting very quickly out of hand.