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Weight gain of U.S. drivers
has increased nation's fuel consumption
E. Kloeppel, Physical Sciences Editor
photo to enlarge
by L. Brian Stauffer
H. Jacobson, professor of computer science, and
his former graduate student, now a professor
at Virginia Commonwealth University, have found
that weight gain of U.S. drivers has increased
the nation's fuel consumption.
Ill. — As
American waistlines have expanded since 1960, so has their consumption
of gasoline, researchers at the University of Illinois at Urbana-Champaign
and Virginia Commonwealth University say.
Americans are now pumping 938 million gallons of fuel more annually
than they were in 1960 as a result of extra weight in vehicles. And
when gas prices average $3 a gallon, the tab for overweight people
in a vehicle amounts to $7.7 million a day, or $2.8 billion a year.
The numbers are added costs linked directly to the extra drain of body
weight on fuel economy. In a paper to appear in the October-December
issue of the journal The Engineering Economist, the scientists conclude
that each extra pound of body weight in all of today’s vehicles
results in the need for more than 39 million gallons of extra gasoline
usage each year.
“The reason we looked at this issue was that gas prices hit an average
exceeding $3 per gallon in September 2005,” said Sheldon H. Jacobson,
a professor of computer science and director of the simulation and optimization
laboratory at Illinois.
“This was the highest recorded level in the United States. We thought
there must be some way that we could determine how to quantify the effect of
being overweight on fuel consumption. We felt that beyond public health, being
overweight has many other
Jacobson presented the challenge to Laura A. McLay, who was a doctoral
student in his laboratory at that time and is now on the faculty at
Virginia Commonwealth University, and they pursued the issue through
his funding with the National Science Foundation.
Their conclusions are based on mathematical computations drawn from
publicly available data on U.S. weight gain from 1960 to 2002, a period
in which the weight of the average American has increased by more than
24 pounds, according to data from the U.S. Department of Health and
By 2002, 62 percent of adults were overweight with a body mass index
of between 25 and 30; more than 30 percent were considered obese with
a BMI exceeding 30.
The fuel-consumption calculations apply only to passenger vehicles,
including cars and light trucks driven for non-commercial reasons.
Ruled out were other factors such as increasing the weight of cargo
or decreasing fuel efficiency through poor maintenance. Driving data
collected in 2003 were used to gauge fuel consumption based on weight
gains during the last four decades.
The researchers used three different scenarios that considered not
only beefier drivers behind the wheel but also their passengers, accounting
for individual characteristics such as ages, numbers of people in the
vehicle, and expected weights.
Since 1960, McLay and Jacobson said, the consumption of no less than
938 million gallons of gasoline annually can be attributed to weight
gains of drivers and passengers. Of that total no less than 272 million
gallons are consumed annually as a result of weight gains since 1988.
“The key finding is that nearly 1 billion gallons of fuel are consumed
each year because of the average weight gain of people living in the United
States since 1960 – nearly three times the total amount of fuel consumed
by all passenger vehicles each day based on current driving habits,” McLay
and Jacobson wrote.
“Although the amount of fuel consumed as a result
of the rising prevalence of obesity is small compared to the increase in the
amount of fuel consumed stemming from other factors such as increased car reliance
and an increase in the number of drivers, … it still represents a large
amount of fuel, and will become even more significant as the rate of obesity
Jacobson said, should be considered conservative because they do
not consider many indirect consequences of obesity nor the increase
in the number of vehicle miles linked to more people living in the
United States and owning cars.
reach Sheldon Jacobson, call 217-333-1043.
reach Laura McLay, call 804-828-6052.
original draft of this news release was written by Jim Barlow, who
has since become the director of science communications for the University