I remember doing a research project on obesity last year. The reasons for someone being obese are far more complex than most people realize, but even still, the vast majority of the times the responsibility lies with the individual. But America is a fast-food nation. A child might be more likely to know who Ronald McDonald is than George Washington. Our own schools constantly stress nutrition, and yet the average school serves food that isn't much healthier (and not nearly as good-tasting) as your average fast-food joint. Not to mention the media constantly churns out all these 'miracle diets' that are supposed to make people lose weight without exercise. The key to losing weight is simple: watch what you eat and exercise. But most people lack either the willpower or the motivation to do so. People just want to be able to diet for two days and lose five pounds at keep it off. Unfortunately, it doesn't really work that way. By the way, I would seriously recommend the documentary Super-Size Me by Morgan Spurlock. It really is one of the best, and most-frightening, documentaries I've ever seen.
Then again, there's always the Subway diet.