Global Warming: Is Weight Loss A Solution?

That title is taken from an article of the same name in the peer-reviewed International Journal of Obesity by Gryka, Bloom, and Rolland, themselves from the Centre for Obesity Research and Epidemiology in Aberdeen.

The International Journal of Obesity is not to be confused with the journal Obesity, nor the Journal of Obesity, nor Obesity Reviews, nor The European Journal of Obesity, nor Obesity Research, nor Obesity Management, nor any other of the half dozen titles focusing on this mysterious disease. (Also see this.)

Before we start: when reading obesity “studies” I am always put in mind of The Onion “story” in which busy doctors, worn thin by scurrying about, missing meals, treading hallways and stairways, are perplexed by their inability to discover the source of obesity.1

Anyway, Gryka and pals assembled together a whopping 25 fat folks with type-2 diabetes and stuck them on a “low-carbohydrate, high-protein diet” for six months. Having somebody breathing down your neck and pestering you to stop eating so damn much usually works, as far as diets go, and it worked here, too. The small sample of people lost an average of 10 kilograms (about 22 pounds).

Now it is true that if you were to haul around a 10-kilo weight you will expand more energy than if you did not, all else equal. Expending more energy means sucking up more oxygen, and thus expelling more carbon dioxide. A person with 10-kilo of extra stuffing around the short ribs will thus expel more CO2 than the same person grown svelter.

Therefore, ceteris paribus, fatter people will spew more CO2 than thin ones.

So much is not disputed, and is, in fact, indisputable. But from these simple truths, Gryka and pals conclude:

On the basis of the current data, for every 1 kg of body mass lost, the CO2 production would decrease 3.2 ml min-1. Therefore, an individual who lost 10 kg would produce 32 ml of CO2 less every minute. This would equal to 168 12 l (33.04 kg) of CO2 less in a year, compared with what would be produced without weight loss. In 2008, the global number of obese and overweight adults over 20 years old was 1.5 billion. If all those individuals lost 10 kg and sustained it for a year, the reduction in CO2 emissions would be 49.56 Mt CO2 per year. This would equate to 0.2% of CO2 emitted globally in 2007 by burning of fossil fuels and the manufacture of cement.

Quark RMRWhatever else we learn from this study, we at least are witness to the first researchers to equate human fat and cement production.

To measure CO2 exhalation, our scientists stuck people under a tent like that in the picture (the device is the Quark RMR). These measurements of course occurred in the lab and when the people were at rest (it is difficult to be vigorous lying in a bubble).

Actual CO2 will be very different for normal activities. Thus that 49.56 (and not 49.57 or 49.55) Megaton reduction is already dicey. That 32 ml per minute decrease in resting CO2 is for the very fat, but the authors assume it will be the same for the merely “overweight” and for those, fat or otherwise, without type-2 diabetes. The authors are aware of these criticisms and admit that their “calculations may be slightly overestimated.”

They do not however admit a weakness from the tiny, almost-not-there sample size. To extrapolate from 25 obese Scottish diabetics to the world population is not responsible.

Real uncertainties creep in with the ceteris paribus assumption. Things are anything but equal between a nation of grossly obese and another of thin folk. It costs CO2 to bring all that food to market for the fat nation, but all that “extra” CO2 that is saved in the thin nation is probably more than made up for in the CO2 not taken up by the food.

I mean that as food grows it stores CO2. Plants take it up directly, and our food animals eat the plants, storing more CO2. If people aren’t eating that food, we won’t grow it and therefore the CO2 that would have been taken up is left lingering in the air, trapping heat, and, as the authors say, causing “the extinction of many species, irreversible changes in the ecosystems and environmental disasters like storms, wildfires, droughts or floods.”

People are no different than food animals: they take up carbon because fat is made from carbon. Thus, since fat people store more carbon than thin, it might benefit our precious atmosphere to encourage more people to double dip their potato chips.

This analysis is no more speculative than that offered by our authors. Mine and theirs are probably both wrong, and wrong in ways that are unpredictable and unanticipated. The only difference between the two analyses is that mine does not pretend to posses scientific certitude.


1If anybody can find a link for this, please post it below.

Thanks to Willie Soon for forwarding the original article.


  1. “Therefore, ceteris paribus, fatter people will spew more CO2 than thin ones…”

    All the “fat people” I’ve put an ear to, breath rarely-and in short gasping breathes. Maybe they breathe heavier when downing an entire 9″ X 13″ pan of Chocolate cake? Maybe the climate police should outlaw chocolate cake?
    Contrarily, skinny people who engage in triathlons breathe fast and often. Obama should order Eric Holder to outlaw cycling, swimming, discus throwing, rowing and climbing.
    While Obama’s at it, he could extend his end run around Congress and outlaw all sports including golf.
    Wonder how much Obama exhales when doing his “end runs.” Probably should outlaw that too!
    Terrific write Matt!

  2. By the same logic, people who exercise are even more of a concern – breathing heavily and demanding more oxygen to be converted into CO2. But then again, the obvious flaw is counting only one side of the ledger.

  3. Conversely, they could have concluded that fat people are effective carbon sinks and hence mitigate climate change. Although that wouldn’t be aligned with their funding I guess.

  4. Following the logic of Gryka et al, starving people in third world countries can help Al Gore save the planet by continuing to starve. I’ve noticed that Al has gained a few pounds but, then again, he can afford to double dip by purchasing carbon offsets.

  5. So, .2% of a gas that occupies .04% by volume of the atmosphere. Seems to fit right in with the
    EPA’s bid to restrict ozone which makes up .00006% of the atmosphere. If it’s all the same to you and the EPA, I believe I’ll concern myself with something else.

  6. Briggs, your instincts are correct – human beings (whether fat or thin) are a part of the carbon cycle, by which carbon cycles between CO2 and “fixed” forms (essentially the organic compounds that make up plants and animals). Changing the number (or size) of human beings is almost totally irrelevant if one is inclined to worry about the concentration of atmospheric CO2 (which, by the way, I don’t, for reasons that would warrant a much longer reply).

    Also involved in the carbon cycle are dynamic (but slow) processes involving atmospheric CO2, dissolved CO2, and various mineral forms of carbon (primarily calcium carbonate) – those processes are additionally complex, not the least because there’s a temperature dependence to the solubility of CO2 in water which complicates the whole CO2/global temperature issue even more.

    If there is one related factor that would justify some concern in the whole “climate change” debate, it is the disruption of the portion of the carbon cycle that involves “fixed” carbon in the form of fossil fuels (primarily petroleum, coal and methane). By generally accepted theories, the rate constant for the formation of fossil fuels (from CO2 via plants and such) is on the order of millions of years; by contrast, the rate constant for turning fossil fuels into CO2 by combustion is on the order of fractions of seconds. For all practical purposes, once that stuff is burned, it ain’t coming back (as we all know).

    But again, that’s only a concern if a) you’re worried about atmospheric CO2 levels (which I’m not), or b) you’re worried about depleting all our stores of decayed dinosaurs (which by earlier predictions should’ve have happened decades ago, but still hasn’t come close to happening).

  7. “To extrapolate from 25 obese Scottish diabetics to the world population is not responsible.”

    Epidemologists do this all the time when it’s to their benefit. Only when the results go against them do they declaare the results are invalid due to the small sample size. My favorite example of this is the British Whitehall study on smoking. About 7000 British civil servants participated in this intervention study. They were divided into an intervention group and a control group. The intervention group was nagged to quit smoking, eat better and exercise more. They reduced their smoking by about 75% and many quit. Alas, the intervention group did not improve their disease or mortality rates compared to the control group. When things didn’t work out the right way the doctors declared the study invalid due to small sample size.

  8. The daily two minute hate against the overweight (obese) continues. There is no logic or science in any of it.

  9. One cannot even extrapolate from 25 Aberdonians to the rest of Scotland, let alone the world.

    I guess Dr Briggs needs to visit Scotland to partake of square sausage, black pudding, white pudding and deep fried pizza to understand the cultural significance of the Scottish diet.

  10. There are on the order of 150 million pet dogs and cats in the US:


    For all practical purposes, if one accepts the shallow arguments of the folks who cranked out the paper that started this thread, those critters are just gratuitous emitters of CO2 (and if you count my dogs, you can toss methane into the mix as well) who are hastening the death of the planet.

    Again, because they are just intermediaries in the carbon cycle, their CO2 emissions are essentially irrelevant (not so the methane emissions, at several levels); nonetheless, I’ve often been tempted to promulgate a fake EPA policy proposal for the forced confiscation and elimination of domesticated pets. The spectacle of the EPA, PETA and the nation’s pet owners at each other’s throats is almost too rich to pass up.

  11. @Stosh from the sticks:

    The contention that “they are just intermediaries in the carbon cycle” is false. Neglecting methane, it would be true if their food were grown without petroleum based fertilizers, insecticides, herbicides, etc. and were not trucked from the field/slaughterhouse to the processing plant to the store to your house. The same holds for those who burn more calories due to physical exertion (whether for purposes of “fitness” or because their job/lifestyle involve it). The supplying of food to an American, regardless of whether that American has two feet or four, is an extremely fossil fuel intensive process.

    It’s also the case that moving people, especially by cars, would be less fossil fuel intensive were those people to weigh less than they do. Vehicle rolling resistance is directly proportional to total weight as is energy required to accelerate a vehicle or lift it up a hill or into the air. For a car, below a (very variable) speed of around 35 m.p.h. to 45 m.p.h., rolling resistance is the primary external force to be overcome to achieve propulsion.

    While I don’t think we’ll overcome our reliance on imported fossil fuels or meet the goal of 95% reduction of CO2 emissions by attaining a unified national goal of obesity elimination, it’s clear that we’d burn less fossil fuel and emit less CO2 by doing so. Whether it’s anyone’s business mandating it is a completely different question.

  12. Off topic. (Anyway, I don’t like to criticize a paper that I haven’t read.) I notice that someone donated the book 水滸傳! I hope you’d enjoy it. I’ve only read one Chinese classic novel in English, and I would never do it again. The meanings of idioms are often lost in translation.

  13. Rob Ryan,

    You are of course correct – a grossly obese individual subsisting entirely on home-grown victuals fertilized by his/her own manure will have less of an effect on carbon emissions than a wonderfully lean individual who drives 10 miles every second day to the nearest Whole Foods to stock up on his or her favorites.

    But I don’t think that was the point of the article.

    While I can’t fault any technical details you bring up, I see them more as an indictment of “first world” society as a whole: unless you’re Ted Kaczynski, pretty much anything you do – take ballet lessons, play little league, troop out to the city limits to protest the proposed coal-fired power plant – is going to have a cost in carbon emission. That’s a corollary of the fact that living in a technologically-advanced society requires energy, and (pace wind and solar advocates), unless you build a bunch of nukes, that energy is going to come from the combustion of carbon.

    Minimal life-style changes may reduce those carbon costs at the margins, but significant decreases would require that we live totally different lives – I have no problem with folks advocating that course of action, as long as they’re honest about it. I do however think it’s largely pointless from the standpoint of global temperature.

    I’ve always been amused by the apparent belief of the “warmist camp” that global warming causes everything (see as an example), but I’ll now have to add to that contention that everything causes global warming as well, at least in the “first world”. But yes, because pets are part of our society, and their support requires the same energy sources that ours does, there is a carbon footprint associated with them. As is usually the case when I try to extrapolate to the absurd, reality seems to catch up, and (if it hasn’t happened already), I expect we’ll soon see calls to criminalize pet ownership as another necessary step to save the planet.

  14. Stosh from the sticks,

    Unfortunately, as the developing world (especially India and China, but also Brazil and Indonesia, etc.) aspires to a more “American” (or at least European) lifestyle, they will also be using and competing for fossil fuels. “Drill here, drill now” will not solve our supply problem, but rapid price shocks will force us to do so. I’d prefer to taper off gradually and reduce our fossil fuel consumption by, say 5%/year. In this scenario, relatively small progress is helpful. I’ve outlined a bunch of such items in various posts on my blog. Admittedly, a national obesity elimination goal will not get us to the promised land.

  15. I have always suspected that fat peope exude more methane than thin people do. However, I don’t have the scientific data, and this may be my own prejudice speaking.

    But, methane is a more potent greenhouse gas than CO2.

    We should be examining gaseous releases from both ends.

  16. Rob Ryan,
    You surprise me.

    You seem to be implying that it is more virtuous to store carbon in the earth, than to release it into the air, paired chemically with its soulmates, oxygen and its twn brother, also called oxygen.
    Why do you believe that?

    Do you have evidence that a very slight increase in CO2 emissions warms the atmosphere?
    Perhaps more importantly that a slightly warmer world would be worse than a slightly colder one?

    If you have such evidence, do you then have evidence that it would be better to attempt to completely change the world economies to reduce human CO2 emissions and can you express that all in a detailed net cost/ benefit analysis, free of all warmist and skeptical distortions?

    Finally, please also consider the net costs and benefits of the alternative of just lumping the downsides, rejoycing in the upsides and just, well, getting on with life.

    Or ar you just a denier?
    Do you deny that the climate always changes and that humans can do very little to change that?

  17. “By the same logic, people who exercise are even more of a concern . . .”

    Sorry, guys, I’m burning up your planet. 🙂 I’ve lost 35+ pounds since starting my exercise routine last year. I have to say I’m feeling pretty good about it. I’m sure when I realize all the lives I’ve put in the balance by heating up the planet, though, I’ll feel pretty bad about it.

  18. People are no different than food animals: they take up carbon because fat is made from carbon. Thus, since fat people store more carbon than thin, it might benefit our precious atmosphere to encourage more people to double dip their potato chips.

    Since fat is mainly long-chain hydrocarbons (themselves mostly carbon by weight), if everyone on the planet carried around just one extra pound of fat, that would sequester 6.5 billion pounds of carbon (plus or minus)! 😀

  19. This is a correction to my previous comment. The British Whitehall study was only 1445 civil servants total. I got my studies mixed up. My excuse is that I am growing old and senile.

    What really upset the doctors about the Whitehall study was that the intervention group had significantly more cancer deaths that the control group. This was contrary to the expected results where the healthy living group was supposed to have fewer cancer deaths than those disgusting smokers. The conventional wisdom is that cancer is caused by environmental factors, so if the healthy living group had more cancer, there must be something wrong with the study.

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