That's interesting; your experience is certainly very different from mine. I teach about 80 freshmen and sophomores every term, and about 5 percent of them are morbidly obese, another 5-10 percent significantly overweight and another 30-35 percent somewhat overweight. Many's the time I've tried to have a conversation with one after class while walking up only two floors' worth of stairs, only to be see him stop before we get there to catch his breath, then seriously suck wind once we get to the second floor where my office is.
I'm in the Midwest, where the problem has always seemed to me to be much worse. In CA young people seem to be in better shape, as they do in NYC. In fact, the last time I was in the Bay Area, I made a point of looking and hardly saw a single seriously overweight person.
Here in N. Fla, they are out all year long, and almost all young men that age would find they were forced to work at something that was pretty physical and required them to move it, like construction, construction, construction...and the military as well! Not many young white men here could afford to go to college, but they are not dumb, not at all...