It's part of the thrill of puberty to know that at fifteen, your parents know nothing, and to discover at twenty - they have learned a heck of a lot in five years!
All you can do for any child in any situation is to lay it out for them, and hope they listen.
Initially of course, they don't, until enough time has passed for sensible advice to appear to be something they thought of on their own.
Any time he moans about feeling tired etc., gently remind him of the doc's advice, but keep the doc's name out of it - as though it's something you just thought of. it wil get through in the end - takes a lot of patience.