You want a "fat shock", go visit China. Or at least, go visit China of 13 years ago when I went--there were some pudgy kids there, probably due to the American fast food joints that were popping up.
It was hot in the summer, everyone was walking around with their shirts half pulled up. Very, very few overweight people. Reminded me of old footage of the US from the early 1900s or so.
Not all that surprising. They mostly eat veggies, and their "sweets" are quite a bit less sugary than ours. Saw basically nobody running or working out though, unless you count trying to walk across a road with their insane traffic (makes NYC look like a polite parking lot). One other factor is that they have a ton of smokers so that probably helps with keeping weight down somewhat (again, reminds me of the old days in the US).
I flew back in on layover in Jersey and everyone looked like they'd been inflated with an air pump, it was crazy. And being somewhat overweight myself, I'm sure that's how I looked to the Chinese