Sociological Fat Reduction

It's been apparent for years now: Increasingly, Americans are fat. It's hard on the health care, the economy, the sidewalk, and couches nationwide.
The most popular finger-pointing is at the fat people themselves. Calories in, calories out, these people have a large positive balance. "You chose this." complain the critics. Well, yes and no.
Yes, people that are fat would be less fat if they exercised more and ate less and better food. However, lousy food is cheap (and subsidized), transportation is laid out to favor cars over walking and trains, and manual labor is mostly replaced with office jobs. We're paying people to gorge and not move. And being fat doesn't make one a horrible person.
Encouraging mass transit, walking, and biking would improve health in the country, and furthermore, would make us slightly wealthier. Wealth is not just money, gold, or a big house, but also the power of life and health. A healthier person can do more to make money, and will live longer to enjoy it.
So why haven't we done that? It conflicts with our ideology of private powers. Mass transit would have to be paid by everyone, through taxes, and operate everywhere, to be really effective. Taxes are unpopular. "Why should I have to pay for other people's choices?" people gripe. Meanwhile, roads are subsidized for cars, which people tolerate because cars are privately owned.
On the food end, a set of subsidies have encouraged the production of some crops over others, and a large business complex is dedicated to getting people to eat as many of these as possible. (More eating equals more dollars.) A physician working for the FDA points out that snack foods are researched carefully to be hyperpalatable. It tugs at every instinct we have to accumulate resources for a famine that will never come. It encourages a cheap high that wears off in an hours time, and disrupts all signals that say that you are full and to stop.
And further, marketing is often designed to confuse people's instincts to look for healthier food. The term "organic," assumed by consumers to mean a higher quality food grown without synthetic chemicals, has been found to be not any more nutrious, and in some cases, completely meaningless altogether.
In a world where one practically needs a chemistry degree and a culinary arts degree to eat smarter, and exercise is pushed as something you need an expensive gym membership to do properly, is it any surprise when people shrug, open up another bag of chips, and go watch TV?
Expecting this to change just because you said so is insanity: expecting different results from the same input. Park the car and walk instead. Flex at your desk. Encourage walking, city density, buses and trains. (Buses and trains help if you walk to them. They don't go to your house, and they don't totally go to your workplace, but they bridge the gap, and you walk the rest of the way.) Encourage people to eat more raw vegetables instead of chips. Encourage home cooking. If you own a business, set up a bike-locking area in the parking lot.
To some degree, we're in this together. Policy has implications, and if you give what you always give, you'll get what you've always got.