I base my statement on personal observations.
1. Next door are two high school age girls. Both are large but not fat. Both are athletes and the oldest who is a junior is something of a softball team star. They are of the size of those soriety sisters pictured. It seems that the generation is well nourished since birth and the body form reflects that fact.
They are large, big. Not overweight, not obese.
2. My grandson is the same age. He is also large. He is a card carrying nerd couch potato but while big neither flabby, overweight or obese.
My finding based on observations is that the current crop of teens is just big........ Rubenesque
Is it bad food with lots of carbs and sugars? It is depressing that Americans are getting more genetically inferior in every way.