Can a treadmill help you save at the pump?

Roland Jones Business news editor • Profile • E-mail

A new study that received a lot of publicity last week contends that Americans are wasting billions of dollars every year on gasoline because of the growing size of their waistlines.

Yes, the laws of physics still apply when it comes to driving — the fatter you are, the fatter your fuel bills will be, as it takes more power to propel you and your car down the road. But before you jump onto a treadmill to lose a few pounds, there might be a lot of easier ways to save money at the pump.

“When you start talking about a 1 or 2 percent change [in fuel efficiency], you can get that from a lot of other things, like closing windows and reducing drag, or pumping your tires a little bit harder to reduce rolling resistance,” said Marc Ross, professor emeritus of physics at the University of Michigan. “It’s a long list.”

The obesity rate among U.S. adults doubled from 1987 to 2003, swelling from about 15 percent to more than 30 percent. At today’s gas prices, that means an additional $2.2 billion squeezed out of our wallets at the gas pump each year, according to the study by Sheldon Jacobson, an industrial engineer and researcher at the University of Illinois at Champaign-Urbana and Laura McLay, one of his doctoral students.

“The obesity epidemic is having an economic impact on fuel consumption,” Jacobson told CNBC last week. “We often hear of obesity having a health impact, but now we have a socioeconomic impact.”

Certainly, only those that deny the laws of physics would say no relationship exists between body weight and fuel efficiency.

The same effect already has been detected in airplanes. Research from the Centers for Disease Control and Prevention has found that heavy fliers have contributed to higher fuel costs, which in turn is eating into profit margins or deepening losses. There has even been talk of charging airline customers by the pound.

Outside experts say Sheldon’s calculations probably are correct but that the impact of body weight on fuel efficiency is minimal, and drivers would do better to improve the way they drive instead, driving at a moderate pace, braking more slowly, observing speed limits and removing excess baggage from the trunk of their vehicle.

“I also think driving patterns could also be significant,” said Ross, the the University of Michigan professor. “Stopping is really a tremendous fuel user, so one suggestion is anticipate when people ahead are stopping and let your car coast to a more moderate stop instead of braking hard.”

Losing weight would certainly help your fuel efficiency, but a greater responsibility for fuel economy lies with automobile manufacturers, Ross said.

For years they have used advanced alloys to make their vehicles as light as possible, but there is still scope for more fuel-saving improvements, such as regenerative braking — a feature in the Toyota Prius that recovers energy from braking and stores it in a battery for later use.

Drivers can also improve fuel economy using tires with a lower rolling resistance, or engines with less torque, or horsepower. But will consumers turn away from the big, powerful engines they have loved for so long? Fat chance, says Edward Lapham, executive editor at industry weekly Automotive News.

“Americans like to squawk about fuel economy, but they still want powerful engines,” said Lapham. “It’s why automakers are scrambling to lose the weight in their cars. Since the first oil crisis 30 years ago automakers have been using lighter and lighter materials to improve fuel efficiency. They struggle to get 10 pounds out of [the weight of] a car’s brakes, but if the consumer weighed less it would help too.”

Jacobson points out that a little belt-tightening could help Americans save money on gas. His study shows that if every American driver lost a pound of fat it would mean 39 million gallons of gasoline saved a year, although that’s still a drop in the 130 billion-gallon ocean of gas Americans use each year.

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