Heavier people mean weightier vehicle emissions

Between 1970 and 2010 the average weight across all overweight and obese American men and women increased approximately 5 kg and 6 kg, respectively, and that has added to the fuel needed to transport them, and greenhouse gas emissions in turn. Image copyright Neil Hester, used unaltered via Flickr Creative Commons license.

In case we needed any reasons other than health to watch our weight, a team at Carnegie Mellon University in Pittsburgh, Pennsylvania, has found some. Michelle Tom and her co-workers have looked at how our extra weight adds to the cost and carbon footprint of transport in the US. From 1970 to 2010, the extra fuel needed to carry overweight passengers’ ‘excess weight’ cost $103 billion in total. That in turn created extra greenhouse gas emissions over the 40-year period equivalent to half a billion tonnes of CO2. “Obesity is not just a public health issue, but also has implications for natural resource use and environmental degradation,” Michelle told me.

Weight is important in vehicle fuel use, with developing lighter cars playing a key role in recent efforts to make them more efficient. Working with PhD supervisor Chris Hendrickson, Michelle is studying the strain our heavier societies put on our resources, and therefore tackled the fuel burden from extra weight. “There have been headlines about the health issues associated with people being overweight and obese, but there has been very little analysis of what this means in terms of things like fuel use and calorie intake,” Chris noted.

Michelle pulled together data for personal vehicles, public transport and aircraft, including how many there are, how full they are, and how much fuel they’ve used. And thanks to efforts made to lighten vehicles, she also had access to good information on how weight affects fuel consumption. She could bring this together with records of the US population, how many of them drive, and how much they exceed the highest ‘normal’ body mass index. Combining all this with data on vehicle greenhouse gas emissions and fuel costs meant Michelle could calculate how heavy the impact of heavier people has been.