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Sheldon Jacobson, expert on statistics related to travel

1/30/2012  8:00 am

Sheldon H. Jacobson, a U. of I. computer science professor, and graduate student Douglas M. King are experts on the relationship between obesity and automobile travel. They recently discussed the new statistics indicating that obesity rates in the United States leveled off in 2009-2010.

You have been studying the relationship between obesity and automobile travel for some time.  What have you found?

image of professor sheldon jacobsonOur initial research (dating back to 2006 and updated in 2009) measured the impact of obesity on automobile fuel consumption in the United States.  We estimated that 1 billion additional gallons of fuel are being used in noncommercial vehicles purely because American drivers and passengers weigh more than they did in 1960. Our most recent research reversed this analysis to estimate the impact of automobile use on obesity rates. In an article published in 2011 in the journal Transport Policy, we identified a strong correlation (about 99 percent) between how much people in the United States drive and obesity rates over the past decade.  In other words, as we choose to drive more, obesity rates climb.

What does this recent research relating obesity and automobile travel suggest?

If each automobile driver in the United States drove 1 less mile per day, we would observe a drop of 2.16 percent in the obesity rate after six years. This drop would translate into 5 million fewer people being classified as obese in the United States. Given that the average person classified as obese spends an additional $1,500 in annual health care costs compared to the average-weight person, this would result in an annual health care cost savings of $7.5 billion. In addition, more than 3 billion fewer gallons of gasoline would be used annually, resulting in an additional potential savings of over $10.5 billion. Therefore, 1 less mile per day per driver in the United States could result in $18 billion of healthcare and out-of-pocket energy cost savings.

The recently released data from the CDC showed that obesity rates leveled off in the United States in 2009-2010. Were you surprised by this change?

Not really. Beginning in 2001, the number of automobile miles driven per licensed driver began to level off in the United States. Given that our model shows that the strongest correlation between automobile miles driven and obesity rates occurs with a six year lag, this would suggest that that miles per licensed driver in 2001-2004 would translate into a leveling off of obesity rates in 2007-2010.

What do you expected to happen in future years, in terms of obesity rates?

Our model suggests that the obesity rate should remain stable through 2013. On average, Americans drove the most from 2004-2006, followed by a slight reduction in 2007; with a six-year lag, this plateau corresponds to a steady obesity rate from 2010-2013. Moreover, gasoline prices have led people to use their automobiles less frequently. In time, this may translate into lower obesity rates.

What can the average person do to help reduce obesity rates in the United States?

Travel can often be classified as either mandatory or discretionary. Mandatory travel requires the most efficient and expeditious mode of transportation, which is usually the automobile. Discretionary travel provides more flexibility. As society asks that we do more with less and places a premium on our time, it funnels us toward making the automobile our first choice when travelling.  Small changes in this choice, by walking or cycling a quarter of a mile to a store rather than driving, can lead to enduring changes in obesity rates.  Given the growing costs associated with obesity, we are in a position to make better choices that can benefit not only society, but ourselves as well. 

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