The number of gyms has skyrocketed in the past few decades, though. Back when the obesity epidemic really took off ca. 1980, "the gym" was a place inhabited primarily by bodybuilders and professional athletes. Regular folks were mostly doing calisthenics/aerobics, often at home following along with Jack LaLanne or Jane Fonda. Today, Planet Fitness is a ~5.5-billion-dollar company.
Which is why I'm curious about time/scale of effect, and what exactly is meant with "Americans do more exercise than ever".
One indicator is # of gym membership: ~30m->~70m in last 25 years, from 10% of population to 20%. Hard to say how much of that is due to gyms getting better at selling memberships because we know they oversubscribe. But per capita figures still suggest that vast plurarity of Americans, the average American, likely 1.5SD / 80%+ of population, probably don't have habit of regular exercise that would overcome effects of increasingly sedimentary life style. So should be ber surprising that obesity continues to increase.
I haven't been going to the gym in a while, but when I did there were a lot of people mostly looking at their phones and not doing much exercise. It was noteworthy when I ran on the treadmill that I saw other people actually running on them instead of merely walking.
I'd guess that many people going to the normal gyms aren't getting much out of it. Combined with the drive to and from the gym, and often getting a snack or something along the way, I have doubts that going to the gym is an efficient use of their time.
(the expensive, specialized gyms like Crossfit or climbing that cost much more are completely different)
