If junk food was more expensive, less people would want to buy it. If less people bought it the obesity rate would go down. Less people would buy junk food just because they want to and they would only buy it for a special treat like for parties or the cinema.
I watched a movie called "Food Inc." recently and one that spoke of childhood obesity in our country. Really, it comes down to the food companies. They have too much power over us and our farmers. They don't treat us with much care and thought. They subside junk food so it's cheaper so we buy it. But really, if we just taxed the food companies more for their practices they'd be forced to sell better quality food and if we subsided the price on healthy foods we'd see our lettuce, apples, tomatoes, and all that jazz be so much more affordable.
So many people buy doughnuts, ice cream, and Dr. Pepper without even thinking about it. But I believe if junk food was priced higher, people would think; "Oh, is it really worth the money? Even when things like Pepsi, Root Beer, and Mint Chocolate Chip ice cream literally have NO beneficial value whatsoever? Is it really worth it?" It would get people thinking and we could probably benefit as a country and look super awesome. With healthy foods, come healthy bodies. With healthy bodies, come healthy lives, moods, and everything else. If we are all healthy, America would thrive once again.