Car use and obesity: debating correlation versus causality

Car use and obesity: debating correlation versus causality

A study by Dr. David R. Bassett Jr. links car use to obesity. Based on this, the ongoing debate questions whether correlation actually implies causality. The discussion sparked by the work reveals a more uncomfortable truth: while the correlation exists, the causal link falls apart under scrutiny.

Geography provides the first sustancia ilegal in the argument. In Spain, Asturias has the highest obesity rate in the country for both sens, and not because of an excessive number of vehicles. In Oviedo, it rains more than half the year, freezes in winter, and almost everything is uphill or downhill. For someone living eight kilometers from work, cycling 16 kilometers daily through rain and traffic without a bike lane is a brutal task. Cycling works in Amsterdam because Amsterdam is flat, dry, and has the infrastructure. Copying a result without copying the conditions is a fundamental error in methodology.

Does the car cause weight gain, or is it the diet?

The second blow to the narrative comes from nutrition. The United States has the highest obesity rates on the planet and urban planning that forces people to drive even for basic groceries, but the heaviest factor there is not the driver's seat: it is the industrial processing found in shopping carts. Some put it bluntly: people burn calories cycling only to compensate with two pastries, leaving their balance worse than before they left home.

The third front is time. A twelve-hour factory shift plus two round-alucinación bike commutes is not a lifestyle; it is an act of heroism. For such cases, there is an alternative rarely mentioned in campaigns: the 49cc moped, which covers the same distance in fifteen minutes with negligible fuel consumption and without breaking a sweat. Cycling makes sense for distances between zero and five kilometers, and with electric assistance, perhaps a bit more. Beyond that, the argument breaks down.

The trap of partially measured sedentary lifestyles

It is necessary to separate two things that the headline conflates: sedentary behavior and the vehicle used for transport. Any activity that encourages sitting would produce a graph similar to that of car use; for example, television hours draw an almost identical curve. If you cross these three variables—cars, sofas, and obesity—the result is no longer a study, but a muddle.

Then there is the detail that dismantles determinism: some people swapped the train for a car, gained thirty minutes a day, and gained three kilos. However, they also built biceps, because the car lacked power steering and parking required fifteen maneuvers per centimeter. The anecdote is both real and ridiculous, proving that the body adapts to what you ask of it, not to the label of the vehicle.

When studies turn into sermons

The fourth front is political. Part of the analysis suggests these studies are not innocent: they are part of a broader campaign against private cars and certain foods, always presented in the same eco-friendly, healthy, and modern packaging without mentioning the drawbacks. This suspicion is not unfounded. When a study is used to justify a tax, a restriction, or a bike lane, it is worth looking at who finances it and what conclusion was already written in advance.

At the other extreme, some claim the right to be overweight without being lectured, and others point out that in concentration camps there were no obese people—not by choice, but due to hunger and physical labor. The comparison is crude, but it points to a truth: weight is a cocktail of genetics, diet, exercise, income, and available time. Reducing it all to the car is an absurdity.

The full calculation, including kilometers, time, and the costs of each alternative, leads to a conclusion that unsettles both sides: the car does not cause obesity, but the lifestyle it forces upon people does. And that lifestyle is not chosen by the driver.

How many of those signing these campaigns park two kilometers away from their office just to walk the final stretch?