The economic impact of obesity on automobile fuel consumption

Back in 2005, I was a graduate student working with my advisor Professor Sheldon Jacobson at the University of Illinois. Hurricane Katrina damaged oil refineries in the Gulf of Mexico, causing production to drastically drop. Gas prices surged as supply fell.

Sheldon and I discussed fuel economy in the wake of Hurricane Katrina. He noted that one way to improve fuel economy is to remove all the junk out of a car, because lowering the weight inside a car improves its fuel economy on the micro level. He challenged me to quantify this small change in fuel economy. I was a curious and energetic graduate student, and I threw myself into answering this question for the next couple of weeks. During this time, Sheldon pointed out that as a country, people in the United States had gotten heavier. This additional body weight (about 25 pounds for both men and women between 1960 and 2003) was not insignificant. Given that Americans drive so much, this additional weight accounted for a lot of additional fuel usage.  I felt a little guilty because I had a baby whose car seat weighed about 25 pounds (it was one of the safest on the market) and often left heavy bags of cat litter in my car trunk if I was too tired to carry them inside.

After crunching the numbers, the results were astounding: We found that if we put people from 1960 into automobiles in ~2005, approximately 938 million gallons of fuel would have been saved by transporting lower weight passengers, which corresponds to approximately 0.7% of the nation’s annual fuel consumption.

Our paper was published in Engineering Economy. It’s entitled, “The Economic Impact of Obesity on Automobile Fuel Consumption.” You can read the paper here.

Paper Abstract: Obesity has become a major public health problem in the United States. There are numerous health implications and risks associated with obesity. One socio-economic implication of obesity is that it reduces passenger vehicle fuel economy (i.e., the miles per gallon achieved by automobiles, which include cars and light trucks driven for noncommercial purposes). This article quantifies the amount of additional fuel consumed (annually) in the United States by automobiles that is attributable to higher average passenger (driver and non-driver) weights, during the period from 1960 to 2002. The analysis uses existing driving data in conjunction with historical weight data. The results indicate that, since 1988, no less than 272 million additional gallons of fuel are consumed annually due to average passenger weight increases. This number grows to approximately 938 million gallons of fuel when measured from 1960, which corresponds to approximately 0.7% of the nation’s annual fuel consumption, or almost three days of fuel consumption by automobiles. Moreover, more than 39 million gallons of fuel are estimated to be used annually for each additional pound of average passenger weight.

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The paper was published in December 2006. A press release went out in October, a month into my first tenure track position. Sheldon and I anticipated that the paper would receive a lot of media attention. In preparation, we received training from the excellent University of Illinois media team. They helped us develop a series of takeaways and talking points about the paper and taught me how to stay on point during interviews. Sheldon was a lot more eager to talk to the media than I was. He agreed to do the heavy lifting when it came to media engagement.

When the press release came out, the paper received a lot of attention. I received phone calls at home at the crack of dawn asking for interviews for radio programs. I was on television. I was quoted in newspapers. I was on the radio. Journalists asked me how much I weighed during interviews (really!) and one asked me if I “hated fat people.” The Associated Press wrote an article that was published in hundreds of newspapers.  In all, our research findings were reported by news articles in more than 400 online and print newspapers and magazines, and was featured on several national cable news shows and regional radio shows. My interview with WDBJ7, a CBS affiliate in Roanoke, Virginia, appeared on the evening news. It was scary, but overall it was a great experience. Amazingly, I saw references to this paper in the popular press years after the press release. For example, a CNBC quiz asked how much gas is consumed annually due to Americans’ weight gains since 1960. I got the right answer (938 million gallons of gas).

The media firestorm helped me become comfortable with working with the media, despite my introversion. I could see the value of media attention to scientific topics such as analytics, and now I always embrace bringing engineering, operations research and analytics to the public. I am much better at talking with journalists, and I’m happy to say that no once since has asked me about my weight.