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Obesity causes global warming?

Tuesday, April 21, 2009 Posted by Peter Janiszewski, PhD

Such is the conclusion of a recent paper in the International Journal of Epidemiology, which was published online just days ago.

Globally, food production and transportation contribute to 20 and 14% of green house gas emissions, respectively. Given that larger people tend to consume more food to maintain weight, and that excess weight results in greater fuel consumption for a given distance travelled, the authors of the paper use various calculations to predict the increase in green house gas emissions emanating from a world getting increasingly more plump.

Their approach is quite straightforward. They basically compare the needed food production and transport fuel use between 2 populations of 1 billion people: the rather lean United Kingdom of 1970’s to that of its more rotund version today, that is, a ‘normal’ adult (30–59 years) population with mean BMI of 24.5 kg/m2 and 3.5% obese, with a corresponding ‘overweight’ population with mean BMI of 29.0 kg/m2 and 40% obese.

With regards to green house gas emissions from food production (i.e. think methane production from cows), due to a 19% increase in the amount of food required to feed this population, an overweight 1 billion people would produce an excess of 0.27 Giga tons of green house gasses per year, in comparison to their leaner counterparts.

Additionally, the fuel needed to transport this heavier theoretical population is suggested to result in another 0.15 Giga tons of green house gas emissions over the lean population.

Overall, the authors suggest that somewhere between 0.5-1.0 excess Giga tons of CO­2 would be produced by a billion overweight and obese people versus a billion lean people.

Nevertheless, while the notions raised are interesting and do sound plausible, these findings are just predictions made with large assumptions, and do not result from an analysis of direct data.
For example, it cannot be assumed that all lean individuals consume less calories than their obese counterparts – take for example our very own Mr. Travis Saunders who ran a marathon yesterday – he will have to consume more calories than you’d predict to maintain weight based on his size. Additionally, things like carpooling in a hybrid vehicle versus solitary SUV driving is likely to be more influential in the greater scheme of things than weight gain of the passengers.


Edwards, P., & Roberts, I. (2009). Population adiposity and climate change International Journal of Epidemiology DOI: 10.1093/ije/dyp172

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2 Response to "Obesity causes global warming?"

  1. Yoni Freedhoff Said,

    And I imagine Travis didn't run to Boston did he?

    Travis, why are you trying to kill my children's planet?

    Posted on April 22, 2009 at 9:26 AM

  2. Room 5 Toko School Taranaki Said,

    Is food production responsible for 20% of the world's greenhouse gas emissions? I've read that the livestock industry is responsible for 18%. So if fat people become vegetarian they'd certainly reduce their contribution to climate change. They'd no doubt lose some weight too.

    Posted on June 20, 2009 at 12:06 AM


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We are PhD students in the School of Kinesiology and Health Studies at Queen's University in Kingston, Ontario. Our research focuses on the relationships between obesity, physical activity, and health risk. This blog is our attempt to consider the many "cures" for obesity that we read about on a daily basis. Enjoy.


The opinions expressed here belong only to Peter and Travis and do not reflect the views of any organization. Any medical discussion on this page is intended to be of a general nature only. This page is not designed to give specific medical advice. If you have a medical problem you should consult your own physician for advice specific to your own situation.

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