Apologies for the rant but this thread has touched a nerve, please encourage better eating habits in your teens!
I'm with OP.
I have a ds who is 16 and 6'3". He eats good meals and then at 10 pm, comes downstairs and makes himself another meal, like the 5 weetabix.
He has grown about 5" in the last year. He eats much more ont he weeks he works out int heschool gymn at lunchtime, and much less on the weeks he doesn't. He eats when he is hungry, and when not hungry doesn't.
I remember my brother being the same, he had breakfast, snakc, lunch, snack, meal, snack, and second meal later. Snacks were healthy, just needed lots of them!
Ds is skinny and tall. I love teenage boys, I love the gauche adolescent stage in boys and girls actually. I love being there to support them and then letting go and hoping they remember some of the wisdom I've tried to impart over the years, like the teenage version of a toddler taking their first steps.
As to girls, well, dd2 has eaten seconds, thirds and fourths at meals for the last week. We were staying with relatives and it became a standing joke. We were joking about her being about to have a growth spurt, and wondering if we should measure her now...