Fitness activities and being fit are major upper-middle-class (talking social class here, not strictly income) markers right now. There's pressure to be or beco

Fitness activities and being fit are major upper-middle-class (talking social class here, not strictly income) markers right now. There's pressure to be or become fit(ter) if you run in those circles, so you don't seem "other". Not so much in other classes—of course perpetually being about to try some new diet or other is a thing in certain groups, but not the same kind of conspicuous fitness stuff the upper-middle's currently big on. Of course upper-middle culture is fairly urban (aside from their vacation houses on the lake or in the mountains) for a bunch of reasons so the trend is most noticeable there, aside from urbanites trending thinner generally than country dwellers (in the US, at least).