I suspect one of them is some people get shockingly little exercise. When I lived in the suburbs, my daily could often be “walk to car, walk from lot to office desk (taking the elevator instead of stairs), walk from there to car (via elevator), walk from car to home”. Total walking time less than five minutes.
When I moved to New York I got at least twenty minutes of walking to and from the subway every day just going into work. Plus now I walk to the grocery and other stuff.
That doesn’t really explain why obesity has increased. If anything, it is often easier to get by without a car today than 20 years ago. For example, my own city is full of bike paths that did not exist then.
They did add a bunch of bike paths in my town too, yet I’m 5 minutes by car from my nearest grocery store, but by bike have to cross a bridge with fenced sidewalks and no shoulder, ride on a 80km/h+ road, and a bunch of other BS just to get there. Bike infrastructure doesn’t mean good bike infrastructure I guess.
Sure, it’s still not good. But that can’t explain why people are more obese now than a couple of decades ago, since bike infrastructure was even worse then.
I wonder if part of it is more likelihood to have multiple cars, less likelihood to have someone prepare meals from scratch … or maybe that’s more than a couple decades.
COViD helped me discover a passion for cooking (baking too, but not just baking) so in the last few years my kids have had more meals prepared from scratch, more balanced and nutritious, and a lot more exposure to meals from other cultures.
One of the new tools I got is an air fryer. It’s a really convenient way to make the equivalent of grilled chicken or other foods …. But all too often I find myself feeding it processed junk like chicken strips and frozen fries