system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do Asian countries have a much smaller rate of obesity than the US?
gpt
There are genetic predispositions involved in obesity, but also considerable differences in diet and culture.  

Obesity has been growing a lot in China, as its food supply industrializes and Western practices like using cheap, non-natural sugars in packaged foods increase.  

However, it doesn't seem to be an issue in Japan or South Korea, where cuisine is strongly cultural and not just based on economics.  Food preparation and balance is taken very seriously, in ways that are similar to French and Italian culture, but with very small portion sizes.

There is also a cultural emphasis on shame, so an obese person is more motivated to take whatever measures may be necessary to lose weight, whereas there is more of a rationalizing and individualist view in most Western societies.  

Shaming a fat person is unethical in Western culture while being one is ethically neutral (except in that maybe you cause people who care about you to worry for your health), whereas in Japan, being fat could be considered mildly unethical because you may be embarrassing your family and the people you're associated with.