Obesity is a global issue, not limited to the US (any more.) I think muchof the reason nations are becomming increasingly obese is simple enough: food has become overly convenient. If you only have to open the package, or microwave something you're gonna eat food which is by definition more convenient than food that requires preparation time. Convenient foods are usually at the same time more convenient, also more unhealthy.
We also aren't teaching cooking any more in schools. Why teach how to prepare actual nutritious meals if everyone's just gonna pop something in a microwave, or rip open a plastic bag to eat.
