The environmental scourge of obesity

Last month, I was reading an article in The New Yorker about calculating carbon footprints. The article referenced an article in the New Scientist which they said "suggested that the biggest problem arising from the epidemic of obesity is the additional carbon burden that fat people—who tend to eat a lot of meat and travel mostly in cars—place on the environment." The article, which appeared in the June 30, 2007 issue of the magazine, is by Ian Roberts, a professor of public health at the London School of Hygiene and Tropical Medicine. It is only available online to subscribers to the magazine, but I think it's just as well, as it is a truly shameful excuse for science "journalism."

Here are Roberts's key points (please note that he does not cite any sources for any of this information, and much of it is either highly suspect, or I know it to be incorrect):

-The U.S. has the world's highest rate of obesity and also has the highest per capita carbon emissions, and this shows that obesity and carbon emissions are linked.

-Obese people eat 40% more calories than lean people, and food production accounts for 20% of greenhouse gas emissions

-I was going to summarize this next part, but realized that I could not possibly convey its awfulness by doing so, and so I will just reproduce it:

Consider what happens to someone on the path to obesity. It might start when he (or she, of course) decides to drive rather than walk the half mile to the office, just to get there a few minutes earlier. A year on he might have gained a kilogram of fat, and as the weight continues to pile on he eventually finds it harder to move around and is loath to walk or cycle anywhere[...]By now he'll be suffering low self-esteem, which leads to comfort eating and perhaps heavier drinking, too. He'll even notice a load on his household energy bills: his greater bulk and higher metabolic rate will cause him to feel the heat more in the globally warmed summers, and he'll be the first to turn on the energy-intensive air conditioning.

In looking for the New Scientist article, I had come across some other media reports on the environmental impact of obesity, most of them referencing this study by a University of Illinois Computer Science professor and a graduate student. Unfortunately, I wasn't able to read the original article, as none of the libraries I have access to subscribe to The Engineering Economist, but according to that press release, the study showed that weight gain by Americans since 1960 now causes us to consume an additional 938 million gallons of gasoline per year. That sounds pretty bad, right? But maybe not so much when you consider that that represents only a 0.7% increase in fuel consumption over what it would cost if Americans weighed the same now as in 1960. As the authors, McLay and Jacobson, write in the paper, "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" (not to mention the fact that people still opt to drive heavier and less fuel-efficient vehicles). And yet still, the article was widely reported on with headlines like "Expanding waistlines lead to pain at the pump."

It also occurs to me that even if obesity did have a significant impact on fuel consumption and carbon emissions, what would be the logical response to such a finding? Forced weight loss surgeries? Food rationing for fat people? Forcing people to pay for carbon offsets for their fat? Obviously these are all ridiculous ideas, particularly in light of the fact that there are many factors which we can control that also contribute to fuel consumption and global warming.

Although there may indeed be a link between our high-carbon lifestyle and obesity, it seems to me that we ought to be looking at this issue from the perspective of those things we can change. This study for example, finds that taking public transit is associated with an additional 8.3 minutes per day of walking, which if applied to people who now commute in their cars could dramatically reduce obesity rates (in addition to the carbon savings associated with public transit). This is a theoretical model, so its validity is not established, but if it's true, increased funding and use of public transit will result in both decreased pollution and increased health, which sounds like a win-win situation to me.