i know it sounds simplistic, but before linking obesity to viruses and other sophisticated theories, one should look straight to the facts, we eat more in quantities, more processed food.
We are too reluctant to consciously restrict the availability that we face. a point to think about.

We eat more of the wrong foods. But I think it's important to point out that most American's cannot afford to eat healthy.

'most American's cannot afford to eat healthy'
either that or don't have the time to prepare(cook) proper food

Eat more and exercise a lot less. All that sitting around in your car, office and home is not very productive, body wise.

I agree with Debby, ready made foods are cheaper rhan buying a lot of stuff to make your own.