Japanese women's life expectancy is 86.3 years old; No.1 in the world since 1985.
Japanese men's life expectancy is 79.1 years old; only second to Iceland.
If "you are what you eat" holds true, this should mean something is sustainable with Japanese food/diet.
Japanese elderly people that are now reaching 80, 90 or 100 years old are the ones who survived very harsh time; wars and poverty. My grandma always talks how food was not easily available as is now. Probably, they are the ones who had been "undernourished" according to today's nutrition standard.
But they are very healthy. A lot of them still work on the farm.
So there should be other secret than achieving so many kilocalories per day.
Basically, traditional Japanese diet consists of rice (or other grains), vegetable and fish and not much meat or greasy stuff. Besides that, the food was not abundant. Unlike what you would think from "Japanese food" such as Sushi or Teriyaki, traditional Japanese diet has been very simple and not luxurious. People came up with a lot of rules to enjoy whatever was available and to sustain fishing/farming and to sustain their lives.
Some rules for sustainable eating:
* Enjoy the natural taste of the food
* Eat a little bit of everything (30 items per day expected)
* Don't overeat (chew well, stop before you really feel full)
You might know "bento". Traditional bento depicts these rules well. As you see in the picture, there are always something that are harvested in the season (called "shun") such as vegetables, fish. What are right off from the farm/ocean is best. Beause they are best, you wouldn't need much to add to enjoy it. They naturally taste good. Also, bento incorporates small bit of everything. And although there are many items, it's not too much in amount.
Moms make lunch box for kids based on the same philosophy.... Or I have to say moms used to.
Eating habit now in Japan is getting junkier.