Computer scientists study the darndest things, or at least the ones at my alma mater, the University of Illinois Urbana-Champaign, do. They write algorithms to predict presidential election outcomes and March Madness basketball brackets; they analyze aviation security risks; and now their dot-connecting computer codes are pointing an accusatory finger at the automobile for causing America's obesity epidemic. Preposterous! Or is it?Dr. Sheldon Jacobson's team in the simulation and optimization laboratory started its long journey toward that outlandish accusation by gathering data on personal vehicle use because, as Jacobson rightly points out, "Obesity is an energy imbalance, and driving is one of the lowest-energy-expenditure activities we do in any day." Well, maybe not the way some of us cut and thrust through rush-hour traffic, but point taken.

Vehicle miles traveled by non-commercial passenger cars and light trucks were divided by the number of licensed drivers and plotted by year from 1985 to 2007. The study also plotted economic activity in terms of gross domestic product per adult. Then annual obesity rate information was plotted using data that has been collected by the Centers for Disease Control and Prevention since 1995.

Sure enough, all the lines slope up at a similar rate, with VMT/LD rising right along with GDP/adult. The funny thing is, the plateaus that indicate the economic slowdowns of 1990-1991 and 2000-2001 don't show up on the obesity trace until about six years later. This lag is explained by a 2008 Chow and Hall study titled "The Dynamics of Human Body Weight Change," which posits that, after a change in diet or physical activity, body weight achieves steady state after about 2000 days -- 5.5 years. Applying this shift resulted in a 98.4-percent correlation between VMT/LD and obesity rates.

To back up their conclusions, the team pointed to a European study that found the highest obesity rates in countries with the most car use, and an Atlanta survey finding that spending an extra hour per day in a car increased the respondent's odds of being obese by 6 percent.

Turning its numbers around, the U of I team asserted that America's obesity problem would be eliminated if we each replaced 12 miles of daily driving with a more physical means of transportation while continuing to do all the same things. Jacobson knows this will never happen, and notes that "if the changes that lead to obesity are small, the changes that reverse it can be small, too -- but they must be persistent. If every licensed driver reduced travel by one mile per day, in six years the adult obesity rate would be 2.16 percent lower, leading to $16-18 billion in health-care savings."

The Illini study made no recommendations, but Jacobson observed, "Obesity has become a societal problem, so addressing it with societal changes may be called for." Positive examples might include citywide bike-rental plans like Vélib' in Paris; negative examples include London's congestion pricing and parking costs. Or how about this: Keep our cars, but convert them to hand controls, and make occupants pedal a generator set if they want to use their beloved smartphone infotainment systems. Problem solved.