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Does driving make you fat? The intuitive answer to this question is yes, of course it does—sitting in one place for a long time is just generally not healthy for you, regardless of whether you’re sitting in the driver’s seat of a car or in front of a computer screen. The driving-physical health relationship could be a case where intuition actually stands the test of science. Today, the Economist looked at a Univerity of Illinois study that found a 99.6% correlation between increases in vehicle miles driven and increases in the obesity rate. The correlation is staggered by about six years, since that’s how long the researchers believe it takes for changes in diet to have a significant effect on body weight. But the correletion is still there.

On the other hand,

…correlation does not equal causation. And it should be noted that the authors did not control for factors such as diet, income and lifestyle. Additionally, they did not explore the possibility that the larger, and thus more immobile, people become, the more they drive.

There is an interesting statistical link between driving and obesity, but it’s not clear exactly what this link means. It certainly doesn’t automatically mean that taking public transportation is physically healthier for you than driving. As Anne Lowery noted in Slate, any long commute is bad for you, no matter what mode of transportation you’re using. The problem isn’t driving, so much as having to cover long distances on a daily basis:

In the past decade or so, researchers have produced a significant body of research measuring the dreadfulness of a long commute. People with long transit times suffer from disproportionate pain, stress, obesity, and dissatisfaction. The joy of living in a big, exurban house, or that extra income left over from your cheap rent? It is almost certainly not worth it.

Even if the Illinois study tells us little about how driving and obesity impact one another, it is consistent with the research trends that Lowery identifies, and reinforces the notion that low-density living can literally be soul-crushing. But even that conclusion is problematic—not everyone can live in the middle of a major city, and the existence of vast, exurban sprawl proves that not everyone even wants to. The commuting-public health correlation is one that eludes a specific policy solution—until everyone lives within a 10-20 minute journey of their workplace (something which would only happen due to near-fascistic, zoning regulations that we’ll hopefully never see in this country), it’s a problem that we’ll likely be stuck with.