7 Comments »Posted on Wednesday 22 April 2009 at 6:41 pm by Jacob Aron
In Climate Change & Environment, Getting It Wrong

Getting the Tube home last night my eye was drawn to a man reading The Sun. “Fatties cause global warming” screamed the front page. “Oh really?” I thought. “And here I was blaming it on CO2 emissions.”

The news comes from a paper in the International Journal of Epidemiology, entitled Population adiposity and climate change. Adiposity being an overly-scientific term for “fatness”, that is.

Dr Phil Edwards of the London School of Hygiene and Tropical Medicine and his colleague Ian Roberts modelled two possible populations, one “normal” with 3.5% obese people and another “overweight” with 40% obese, as measured by a Body Mass Index of 30. Both population consists of a billion people. They say that the normal population reflects the UK in the 1970s, whilst the overweight population is the prediction for 2010.

By estimating the energy required by both populations they found that the overweight population would require 19% more energy than the normal population. This of course means the overweight population would need to consume 19% more food. Producing this extra food would result in 270 megatonnes of extra greenhouse gasses (meaning CO2 as well as other gases like methane) being released into the atmosphere.

An overweight population would also release further greenhouse gases through increased reliance on transport. Newton’s laws of motion tell us that moving a heavier mass requires a proportionally larger force, so we would expect heavier car drivers to use more petrol. Overweight people are also more likely to drive rather than walk, compounding the effect. In total this would add another 170 megatonnes of greenhouse gasses to the atmosphere.

All of these figures are really extended back-of-the-envelope calculations. In the paper, the authors admit to making many assumptions about the two populations, such as keeping everyone of the same sex at the same height, and using identical levels of activity for both normal and obese people. As such, I wouldn’t take these figures as literal, but they do indicate that an overweight population has some effect on climate change.

Does this research mean then that a global diet is in order? Eat carrots, stop climate change? No. Food production accounts for only 20% of emissions, according to the paper, so in a planet of one billion people as imagined by this model we’re still left with 6000 megatonnes of greenhouse gasses being pumped out by other industries.

Tackling climate change requires a transformation in the way we consume and generate energy. The Sun story paints it as a problem caused by “fatties” – an easy scapegoat, but we’re all to blame. The obesity crisis is an issue that must also be tackled – nearly half of the population obese by next year is insane – but it’s not a magic bullet for climate change. Nothing is.


  1. 7 Comments

  2. I’m going to go out on a limb here and suggest we credit the Sun and its readers a sense of irony. I don’t think anyone will read that and think ‘brilliant, I’m thin so I may as well go and turn on all the lights in my house, then go out in my SUV and try and run over as many fatties as possible for the sake of the planet.’

    By Sam Wong on Wednesday 22 April, 2009 at 7:59 pm

  3. Hmm, maybe if the story wasn’t on the front page of the paper I’d agree, but the way it was presented implied it was big news – problem solved, the fatties did it!

    By Jacob Aron on Wednesday 22 April, 2009 at 8:12 pm

  4. I just read the original article, in defence of the Sun it does include the information that food production only accounts for 20% of carbon dioxide emissons + includes the quote “We are not just pointing the finger at fat people”.

    But then again, the headline “Fatties cause global warming” may be misleading..

    By Seth Bell on Wednesday 22 April, 2009 at 11:58 pm

  5. what about the fact obese people may be more likely to drive or get the bus for distances short enough to walk or cycle?

    By liz on Sunday 26 April, 2009 at 12:42 pm

  6. Liz: that fact is actually covered in the analysis.

    By Jacob Aron on Sunday 26 April, 2009 at 1:04 pm

  7. There’s also the fact that obesity is higher in lower income groups who can’t afford pricier healthy alternatives (vicious circle) and so rely on goods which are cheaply imported and/or have a longer production line both involving more C02 emissions etc.

    By Katie Goates on Sunday 26 April, 2009 at 6:00 pm

  8. Plus it’s not individual mass but global human mass we should be worried about, population crisis anyone?

    By Katie Goates on Sunday 26 April, 2009 at 6:03 pm

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