Was the Obesity Epidemic Caused by Cars?

If so, removing Twinkies and Coca-Cola from schools probably won't change things much.

Junk food, video games and a lack of exercise all have received their fair share of blame for the spiraling epidemic of obesity in the U.S. But according to a University of Illinois researcher, public health enemy No. 1 for our supersized nation may very well be the one staple of modern life most Americans can't seem to live without one (or more) of: the automobile...

After analyzing data from national statistics measured between 1985 and 2007, Jacobson discovered vehicle use correlated "in the 99-percent range" with national annual obesity rates.

"If we drive more, we become heavier as a nation, and the cumulative lack of activity may eventually lead to, at the aggregate level, obesity," he said.

This makes me wonder how this correlates across income ranges? My understanding is that the poor are more likely to be obese and less likely to own a car. This might be obscured by simply looking at national statistics.

Obesity is rising across all income brackets (in the US). It could be that obesity is positively correlated across national income levels (the richer a country gets, the greater percentage of their population becomes obese) and negatively correlated across individual income levels (the poorer a person is within a given (developed) country, the more likely they are to be obese).

As national incomes rise, you would expect more food to be consumed and more cars to be purchased per capita. Is increased automobile usage the cause of obesity or greater income? Or both?

(HT Barking Up the Wrong Tree)