The typical diet is also relatively lower in bread (processed carbohydrates...with unnecessary added sugar in the US) and higher in protein. That combination is typical of any structured diet designed around controlling weight gain, such as Weight Watchers.
Fast food is also different. International menus have different items and different sizes. I've seen people express shock about the existence of things like the Triple Baconator or US soda sizes. Drinking a 32 oz of sugar-filled soda is an easy 350 calories right there, and a disturbing number of Americans "don't like water."
Konbini and ramen/soba shops also exist, so there are even more convenient alternatives to western fast food, which are often healthier in the typical portions.
I've wondered about about carb substitution. The rice, and the wheat noodles, why are they healthier? (I can understand rice somewhat: it's less processed, by certain definitions.)
Buckwheat is not wheat, soba noodles are based on buckwheat.
Not sure how large fraction of all noodles they eat are that though. Feels like there is something related to additives and other things that makes people eat more.
Whilst you're correct about buckwheat, just about all soba noodles that I've seen here in the UK are predominantly wheat based (I'm gluten sensitive, so have read a lot of product labels).
When looking for gluten free noodles in Asian supermarkets, I've only really found ones that are rice based with some rarer sweet potato vermicelli varieties.
Edit: after a brief search, I have found some Clearspring 100% buckwheat noodles which I shall have to find and buy. They also sell the more usual wheat and buckwheat version of Soba noodles.
