CARL NASMAN, reporter:

This is Santa Ana, El Salvador, where the American shopping mall and diet have arrived. It's El Salvador's second largest city, but the food and the waistlines are straight out of the United States.

Companies like Pepsi, Coca-Cola, and McDonald's have become part of the local diet. Junk food here is cheap, and it's everywhere, from the mall to the most remote villages.

In cities like Santa Ana, junk food is leading to a very American problem: obesity. But in the countryside, it's causing something different.

We're headed into the mountains about two hours north of San Salvador. Out here, there's still plenty of junk food for sale, but there's little or no access to proper dental care. This mobile clinic is one of the few places to see a dentist. It's run by a local non-profit called ASAPROSAR, which provides free health services in rural areas.

Dentists like Jorge Granillo treat children with mouths full of painful, rotting teeth.