As someone who cooks for a 17 year old who trains for and plays rugby quite seriously the sheer amount of food an active teenager can consume is quite staggering.
It's pretty nuts. I used to eat the same kinds of things I eat now, except I would eat three plates of it, instead of one. Along with around a gallon of whole milk a day...
I was just playing soccer and basketball, not trying extra hard to bulk up for football or anything.