Ask Mr. Green: Does Obesity Waste Fuel?

Hey Mr. Green,

Somewhere you calculated that Americans burn around 50 million gallons of fuel idling their engines while waiting to be served at drive-thru fast-food joints. Since fast food makes people gain weight, how much fuel, oh maestro, is wasted hauling around all our excess flab in cars? —Hal, in Decatur, Illinois

It takes about a billion additional gallons a year to cart our extra human tonnage around in automobiles, according to a study from the University of Illinois that pulled together data on transportation, vehicle types, fuel consumption, and weight to reach this conclusion.

Of course duty obliged me to verify this with my own back-of-the-envelope calculations—a task accomplished thanks to an abundant supply of envelopes from Sierra Club fund appeals. I’ll spare you most of the mathematical details, but the, um, bottom line is that more than two-thirds of adult Americans are overweight, with the average man at about 195 pounds and the average woman 165 pounds. This puts our collective excess poundage at around 9 billion pounds more than if we all weighed in at what our medical gurus consider a “healthy” number.

The EPA says a vehicle can lose up to 2 percent of its miles per gallon for each 100 pounds of additional weight. Using this number and 2010 census data, and distributing our 9 billion excess pounds of outsize adults over our outsize fleet of about 230 million often outsize vehicles that burn an outsize 123 billion gallons a year, I too came up with over a billion gallons per year of extra fuel. Of course not all vehicles will lose 2 percent of their mpg, but for simplicity’s sake my calculation excluded tens of millions of notoriously oversize kids and teenagers, so we’re in the ball park. (The situation may have improved a tad in the past few years, thanks to the efforts of everybody from local school officials banning soda dispensing machines to Michelle Obama’s campaign for healthy food.)

Some observers have noted the chicken-and-egg effect, in that driving all over the place deprives us and our kids of exercise that might help us shed some of that superfluous poundage. It’s always made sense to regard the automobile as a public health hazard because of the number of fatal accidents and terrible injuries, but surely this factor should also be considered by critics of our dependency on the automobile. —Bob Schildgen

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