I have consistently lost weight on both trips I took to Japan despite not necessarily eating very healthily. I think a large part of it is all the stairs/passageways into and out of train stations. Obviously some have escalators but some don't or during rush hour it's easier to just take the steps. In the Bay Area we don't have a transportation system with that kind of infrastructure. New York City's subways would be a bit similar, but most of the stations I've been to there have much fewer stairways.