Sheesh. Yeah, his statistics are probably skewed, but his question is still a valid one.

Reason #1: Everyone drives everywhere. Except New Yorkers, who walk a gripload. But everyone else drives and don't get nearly as much exercise as they could if they walked.

Reason #2: If you think about American food, you think steaks, hot dogs, lots of red meat, deep fried chicken, etc. Compare that to things like Japanese and Asian food that consists of rice, vegetables, tofu, etc. I'm not even talking about fast food here, American cuisine itself isn't all too healthy.

Reason #3: Proportions are gargantuan in America. Everything is supersized.

There are more reasons, dozens of more reasons. But like War Angel already posted, it boils down to people eating unhealthy food and not exercising enough.