Obesity is a national problem, and poor diet and insufficient exercise are recognized as the primary causes. But observers increasingly have pointed to our culture and our built environment as possible contributing factors -- specifically, the relationship of residential setting and urban sprawl to obesity.

This analysis relies on self-reported data that is updated irregularly. However, we used the driver's license data because we have an enormous sample and because we have addresses. These two advantages outweigh any potential bias in the weight information.

We don't see anything right now that shows that there's a relationship between sprawl and obesity.