"Does Driving Cause Obesity?"

On the Freakonomics Blog, there is a post covering the correlation that in places where car use is prevalent, people are fatter. There has been little evidence that there is a cause and effect in play until now. The post is so short and succinct, I quote it below

People are significantly fatter in countries, states, and cities where car use is more common. Mass transit use, on the other hand, is correlated with lower obesity. But there has been scant evidence that public transportation actually causes widespread weight loss — until now. A study of residents in Charlotte, N.C., found that users of the city’s new light rail system were 81 percent less likely to become obese, and reduced their Body Mass Index by an average 1.18 points — the equivalent of 6.45 pounds for a person 5’5″ tall. The study appears in the American Journal of Preventive Medicine.

My own personal experiment of the past few months corroborates this, I definitely and thinner (though weight is only nominally less). Interestingly, increased mass transit use has also reduced my appetite for some reason. Perhaps there is something about transient exercise that moderates appetite as well?