Study: Surge in obesity correlates with increased automobile usage

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.

Sheldon H. Jacobson, a professor of computer science and the director of the simulation and optimization laboratory at Illinois, says that the surge in passenger vehicle usage in the U.S. between the 1950s and today may be associated with surging levels of obesity.

"You can think of obesity as an energy imbalance," Jacobson said. "People consume food, which is a form of energy, and then they expend it in their activities. But if you look over the last 60-plus years, the automobile has become our primary mode of transportation – so much so, in fact, we have literally designed our way of life around it. It is that energy imbalance that ultimately may lead to obesity."

To analyze the relationship between obesity and vehicle use, Jacobson and students Douglas M. King and Rong Yuan looked at annual vehicle miles traveled per licensed driver as a surrogate measure for a person's total sedentary time.

Previously, Jacobson studied the effects of extra driver and passenger weight due to growing obesity trends in the U.S. causing excessive fuel consumption.

Jacobson said this new study reverse-engineers the relationship between weight and driving.

"What we did before was based on physics: You add more weight to a vehicle, it consumes more gasoline, and we burn more gasoline on an aggregate level," he said. "This then raises the question, 'Is the reverse true?' If we drive more, are we going to become heavier as a nation?"

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.

Jacobson chose annual vehicle miles traveled as a proxy for a person's sedentary time because inactivity is most obvious when you are sitting in a car.

"When you are sitting in a car, you are doing nothing, so your body is burning the least amount of energy possible," he said. "And if you are eating food in your car, it becomes even worse."

The sedentary lifestyle that automobile use enables coupled with the prevalent role it plays in increasing the sprawl of our cities, towns and suburbs is the "societal price we pay for always being in a rush to get places," Jacobson said.

"For the last 60-plus years, we've literally built our society around the automobile and getting from point A to point B as quickly as we can. Because we choose to drive rather than walk or cycle, the result is an inactive, sedentary lifestyle. Not coincidentally, obesity also became a public health issue during this period."