Did you actually visit Japanese families, or is that assessment based on what you saw in convenience stores and similar? "Convenience" food and western style food has somewhat increased, but on average Japanese cuisine is very healthy.

I also agree on the stressful work part, but don't quite understand what you mean with "lots of commute on public transit". If you mean the Tokyo-style rush hour traffic where people are literally shoved into the train car, of course that's stressful. But at any other time apart from that, Japan's public transit is enormously soothing and stress-free, both because of culture and transit technology.

Yeah, I'd agree. I think that the Japan's public transportation, even in Tokyo, wasn't at all stressful. Maybe I'd feel differently if I had to be shoved in, but that was easy enough to avoid and even at the times when it was a little crowded for my tastes, it was still a great experience.

Day in day out, everyday in public transit, just sheer noise would not add any lifetime. We stayed at our Japanese friend’s house so we did have exposure to their everyday life. The point I want to make is that many things contribute to a long life, and of course Japanese people are doing most of those things right, regardless of what that might be. I remember watching a documentary about Okinawa people. One thing they mentioned was laughter.