Overweight Drivers Pay Heavy Toll in Emissions

Obesity rates are rising dangerously, as evidenced by a recent report, "F as in Fat: How Obesity Policies are Failing in America 2009." The health cost was estimated at $41 billion, but how many extra tons of carbon are caused by the extra pounds?

The report estimated that 26 percent of the population is obese as poor food choices and inactivity force a continuing loosening of belts. The average adult American weight increased by nearly 25 pounds from 1960 to 2002, per a Center for Disease Control 2002 study.

By comparison, 30 percent of Americans were estimated to be obese by a 2006 study by Sheldon Jacobson and Laura McLay; 938 million extra gallons of gas was pumped to accommodate weight increases that year. The study accounted for only noncommercial cars and light trucks.

Jacobson and Douglas King revisited the topic in a study in 2008, and found that the extra gallons had increased by 200 million to 1.137 billion gallons, or by about 21 percent. The newer study, Transportation Research Part D (Transport and Environment), takes into consideration that Americans have grown about an inch since the control values going off research done by the Center for Disease Control in 1960.

Jacobson expressed that obesity and fuel dependency are tied together, "We cannot hope to tackle one without also tackling the other." Expanding on the emissions information provided by the DOE, the CO2 released by the extra gas pumped in 2008 (per Jacobson and King), would have amounted to over 11 million tons.

Drivers in the four heaviest states (Tennessee, Mississippi, Alabama and West Virginia), according to the 2009 study, collectively consumed an additional 61.7 million gallons of gas because of the added weight in the vehicles, when a formula created by Steve Polzin, director of transit research at the University of South Florida's Center for Urban Transportation Research, is applied. Cars (used as a baseline) consume an average of 0.000011 extra gallons of fuel per mile per 'extra' pound; and the average driver goes 14,500 miles annually. Since larger people tend to buy larger vehicles that eat up more gasoline, the actual gasoline consumption could be much higher.

What kind of footprint does that result in? A gallon of gasoline, according to the Department of Energy's Alternative Fuels Data Center, produces about 20 pounds of carbon dioxide. These four states alone, according to my calculations, could have resulted in 1.19 billion annual pounds of carbon dioxide due to gasoline use alone.

Over in the U.K., Phil Edwards and Ian Roberts from the London School of Hygiene and Tropical Medicine, published a letter in the journal the Lancet discussing the impact of obesity on carbon emissions. They wrote that more transportation fuel energy would be used to transport the "increased mass of the obese population, which will increase even further if, as is likely, the overweight people in response to their increased body mass choose to walk less and drive more."

[originally posted: http://featured.matternetwork.com/2009/8/overweight-drivers-take-heavy-toll.cfm]