Instead of concentrating on the symptoms of fatness - we should look at the root cause.
A food supply in America that makes it difficult and expensive to get fresh food. It's much easier, more convenient and often cheaper to buy crap at a fast food restaurant - than to cook your own healthy food. Furthermore highly-sugarry, fatty foods are very profitable. So supermarkets fill shelves with high-fructose corn syrup mascarading as juice, and breakfast cereal that's full of sugar. It's all crap. It's addictive too.
There's also an emotional root cause component. The culture is so spiritually, culturally, emotionally void in America that people eat to cover up feelings. It's like the fat is a buffer of armour that stops you from tapping into your body's energy.