I see plenty of disgustingly overweight people in that age group.
Putting kids in gym class for 40 minutes every other day doesn't make them fit, living fit makes them fit. Eating healthy, getting exercise daily.
Also, I don't see how you could make the case that people would be skinny 30 years later because they had gym in high school.
The obesity problem in this country is not a generational thing, it's a conditional thing- things are too easy and food is disgusting. There's no need to go outside because for the most part you can get entertainment inside. People of all ages are disturbingly fat.
every other day?
we had gym every day of school, with the exception of one marking period. we did calisthenics, they did some sort of sports. to be honest, i hated it, as i've never been that into sports, but i did them anyway. didn't mind the calisthenics though....and believe me when i tell you i am nowhere near the healthy eater that i should be.
my friends kids....his oldest is 26 now....dude's 6'3, and 180. next youngest......5'8 or so, and well over 200. he's 22 now. then there's the 19 year old. 5' 8 or so again,.....nearly 300.......the youngest is 17.....5'6. he is well over 300.
their father was big, but not grossly overweight. their mother is overweight now, but she wasn't before. i know the parents on both sides, and none of them are overweight.......
gym class is important, as it gets the kids up and moving around.