I used to believe that the Japanese diet is inherently healthier because there is lower obesity in Japan. I've asked Japanese people about this and they say that it's actually quite a struggle for many of them to not gain weight, but they work hard to keep their weight down because that's what's expected of them to fit in.

So now my theory is that lower Japanese obesity is more a result of a strong sense of cultural conformity rather than something inherently healthy about the diet.