I'm not sure how to build a resurgent culture of self-responsibility and sporting physical play in western civilization, except to encourage a few fellow geek friends here and there and maybe a thoughtful slashdotter or two.
Fat and sugar are addictive, borderline poisonous substances. On the other hand, willpower, time and energy are all limited resources. So while you'll probably always find some people who'll have enough of a surplus to stay fit throughout their lives even when constantly surronded by temptations and having to spend on both work and personal life, the same as you'll find the odd fellow who'll quit heroin cold turkey without being forced to, no amount of culture-building will significantly affect obesity rates as long as the cause remains on the shelves of every convenience store.
But then again, comparing fat and sugar to heroin is hardly fair. After all, you can quit heroin but you can't quit food, so cold turkey is not an option. Instead, you have to carefully manage the intake for the rest of your life. Which, to put it bluntly, is a sufficient burden that it's probably more rational to settle for being fat. And that means obesity will remain a major problem until excessive fat and sugar are removed from food by legislation.