Overweight drivers and passengers are responsible for cars on U.S.
roads burning about 1 billion additional gallons of gasoline each year,
according to a new study.
The study, headed by a professor at the University of Illinois at Urbana-Champaign, was based on a mathematical model that tied together federal data on gasoline consumption and weight gain among Americans from 1960 to 2002. It found that Americans are pumping at least 938 million more gallons of gas annually today than four decades ago because extra body weight is dragging down fuel economy.
"We had no idea the numbers would be this big,"
said Sheldon Jacobson, a computer science professor at the U. of I. who
conducted the study with then graduate student Laura McLay.
"We came to the realization that our hunger for food and our hunger for oil are not independent," Jacobson said.
Some 1.7 million cars could be filled with gas for an entire year using the 938 million gallons of fuel that could be saved by trimming down the weight of drivers and passengers, Jacobson said.
Details of the study were released Tuesday. The full study will appear in the October-December issue of The Engineering Economist.
The fuel-consumption calculations were based on passenger cars and light trucks driven for non-commercial uses. The weight of cargo and reduced fuel efficiency due to poor vehicle maintenance were eliminated as factors, according to the study.
The study's findings serve as another reminder that the weight of the average American has increased by more than 24 pounds since 1960, according to the U.S. Department of Health and Human Services.
In the early '60s, the average adult male weighed 166 pounds and the average adult female tipped the scales at 140 pounds, according to federal health data.
By 2002, adult males had bulked up to an average of 191 pounds, and the average weight of adult females had increased to 164 pounds.
Among teenagers, the group where obesity is rising the fastest, average weights for male teens increased from 151 pounds in the early 1970s (when record keeping for teens began) to 164 pounds by 2002, according to the federal health data. Female teens also got heavier on average, from 128 pounds in the early '70s to 140 pounds at the turn of the century.
By 2002, 62 percent of adults were overweight, based on their body mass index of height and weight, and more than 30 percent were considered obese, according to federal health data.
Meanwhile, the average weight of passenger cars has experienced a yo-yo effect.
Automobile manufacturers reduced vehicle weights from 1975 through 1987 in reaction to oil shortages created by the Organization of the Petroleum Exporting Countries, according to the Federal Highway Administration. What was later identified as the "Hummer effect" started in 1987 when average vehicle weights began a steady increase that has lasted through 2006.
Heavier Americans are canceling out some of the vehicle fuel-economy improvements achieved by keeping tires inflated to the proper pressure, tuning up engines and removing unnecessary items from trunks, said McLay.