They don't eat as much rice as you would think as a proportion of calories. Rice portions in most asian cultures can fit in the palm of your hand typically. Lots of veggies, fish and meats too.

Ex: https://thriftynomads.com/how-to-be-a-frugal-foodie-in-japan...

While americans typically have a much higher proportion of food as carbs & fat vs protein & veggies.