[redwall_hp]

Japan's easy: only about 1-in-3 households in Tokyo (and presumably the other large cities, where the majority of people live, are similar) own a car. People walk and take trains to work or to go shopping or eat out. A half hour of walking can burn upwards of 100 calories.

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.

[ein0p]

They have much smaller portions across the board. Their "venti" Starbucks drink is what we call "small" in the US, and our "venti" is simply not available. Might even be smaller than small, it sure seemed like it.

[profsummergig]

> diet is also relatively lower in bread

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.)

[Jensson]

> and the wheat noodles

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.

[ndsipa_pomu]

> Buckwheat is not wheat, soba noodles are based on buckwheat.

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.

[ein0p]

Probably slower absorption. Bread really peaks blood glucose, and therefore insulin.