Car culture makes Americans fat and lazy. 40% of US adults are obese. 80% are overweight.
Walking and good food, yeah, that helps. But trains introduce short sprints into everyday life. It starts with "He's too late, he's never gonna catch it... well I'll be damned, he did it." and pretty soon, you're saying "We can catch it, just run!" Everyone on the train has a shopping bag, because trains don't have huge trunks like a car. You want groceries? Carry it. Good exercise. Trains also remove the road rage from your life, the daily stress of defensive driving in a fast moving freeway full of other angry drivers. Trains eliminate the premature death caused by road accidents which not only lower life expectancy directly, but indirectly as bread winners are taken from families. The car exhaust is gone too. Trains reshape how towns are built, with higher density and less parking. More walking! Everything mushrooms out from the decision to travel with trains. It's little wonder why Japan has the lowest obesity rate in the world.