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.