Weight loss and climate change

Like a large proportion of the world’s population[1] I’m trying to lose some weight, in my case the extra kilos added over Xmas and the associated conference season. As those who know me would expect, this entails frequent (some might say obsessive) weight measurement, and it’s a frustrating business.

After some quick early gains (or rather, losses) I’m now losing weight at a rate of a kilo a month, or so. On the one hand, that’s good. I’ll regain my target weight well before the next round of temptations. And, on a sustained basis, it’s enough to go from obese to the lean side of normal in a couple of years.

On the other hand, measurement-wise a loss of a kilo is swamped by intra-day and inter-day variations due to all manner of causes. It’s easy for my inner weight loss sceptic to say I’m going nowhere, or for my inner optimist to say that I’m so close to the target that I can relax my efforts.

Thinking about that got me to thinking about broader parallels between weight loss and climate change.

First up, the basic physics of weight loss/gain is clear. As far as muscle, bone, fat and so on is concerned, the gain or loss in any given period is determined, pretty much exactly, by the difference between kilojoules digested and kilojoules burned (this source suggests a ratio about 40kj/g).

But as with climate change, water complicates things a lot. Men are roughly 60 per cent water. Although this proportion declines a bit with obesity, my understanding is that more solid body mass is associated with more body water, so we have a positive feedback.

The problem is that, in the short term, fluctuations in body water mass swamp (sic!) the modest changes associated with a positive or negative net energy intake. So, any kind of statistical estimate of a trend is highly problematic in the short run. Nevertheless, in the long run, statistics and physics agree, as they must.

The second problem is that, while the answer to weight loss is simple, it is far from easy. Unsurprisingly, therefore, there is a huge amount of wishful thinking. This is represented on the one hand by fad diets[2], and on the other by technological fixes of various kinds. We can subdivide those into easy fixes that don’t work (most of them) and apparently effective fixes that seem worse than the problem to be solved (stomach stapling and similar).

Seemingly opposite to wishful thinking, but in many ways aligned with it, are impossibility arguments. The archetypal argument of this kind is that we are endowed with a metabolism that gives our body a set ‘target weight’ which we cannot change – dieting or exercise will automatically produced countervailing metabolic changes that render them ineffective in the long run.

So, the problem is clear and, for many, debilating or even fatal. The science is equally clear, but its message is unpalatable to many. Result, delusion and self-delusion on a grand scale.

fn1 Fun fact to check for yourself. For the first time in the history of the world, more people are overweight than are underfed.

fn2. Unsurprisingly, for rightwingers there is a party line on this, as on most factual questions. And, as usual, it is determined as a mirror-image of a caricature version of leftism. Since leftists are seen as bean-sprout eating vegans, the orthodox rightwing diet is high in animal protein and low in carbohydrates. (If you think I’m joking Google Limbaugh + low-carb).

44 thoughts on “Weight loss and climate change

  1. don’t weigh yourself every day.

    smaller plate.

    big nutritious brekky.

    small and slowly savoured evening meal.(with soup)

    lay off the alcocarbs,transfats,cornsyrup sweeteners.

    five minutes every now and then during the day for a bit of strenuosity( i made that word up–it fits)five minutes every now and then soon add up.

    getting older it can be a pain to keep fit but at least you have a body you can use and won’t clag out on you in an emergency.(you never know)

    getting older it can be downright agonising trying to be self reliant if you have allowed yourself to become not fit.

    my two cents.

    you’ll get there.

  2. I think the Prof may have overdone the diet and run out of energy – he hasnt been heard from for days?

  3. Ooh, goody gumdrops. I get to be a denialist.
    Possibly not entirely, in that I’m prepared to concede, in very general terms, that if you eat more you’ll get fatter. However…
    Whatever the aesthetic appeal of unfatness, in terms of the bigger picture it’s just not that unhealthy.
    (1) If you control for social class and activity, greater weight doesn’t have a massive effect on all-cases death rates (see, for example, ‘Obesity: How big a problem? by I. Wikelgren, Science, 1998, Vol. 280 no. 5368 pp. 1364-1367’)
    (2) if you look at the epidemiology, it’s very hard to see any input from obesity. Australian life expectancy has been rising at the rate of three months a year virtually uninterruptedly for the past century (see http://www.abs.gov.au/AUSSTATS/abs@.nsf/Lookup/4102.0Main+Features10Mar+2011). Whatever year you date the start of the obesity epidemic to, and whatever the age group you think it’s concentrated in, I defy you to find any signs of it on the graphs. Yes, of course, you could say that the rise is due to other factors such as better health care or more aggressive medicine and that without it we would be improving by six months a year – hell, if we could punch our present rate up by a mere four times we could all live for ever – but that’s a hypothetical.
    (3) Whatever effect obesity does have is almost certainly swamped by the effect of where you stand in the social hierarchy (see the Whitehall studies, passim).
    If Al Gore is fat, it’s doing him no great harm.

  4. But JQ, eight lose contributes to global warming. Fat people carry trapped carbon in their adipose tissue. Depleting fat reserves through exercise releases CO2. If we all try to lose weight, then the carbon emissions will be catastrophic.

    Hmmm… perhaps fat people should get government subsidies for their carbon sequestration efforts!

  5. I knew it – Prof was lying unconscious after the event depleted of vital nutrients (somehow I dont even believe this myself – he probably rode home afterwards!).

  6. So all of those wilderness conservation decisions and World Heritage declarations by Bob Hawke happened because he went on the Pritikin diet and swore off the grog…

  7. Nobody has mentioned a “snack tax” yet.

    Should the government impose this? If there are obesity externalities (higher health costs, unpleasant scenes on the beach) a Pigovian Tax is warranted.

  8. Great post.

    It is also strikes me that the science of weight loss is as poorly communicated as the science of climate change. I know I could lose a few pounds but this BMI measure doesn’t work cause I am tall, also I don’t really understand the cost/benefit equation, having a lower weight reduces my risk of heart disease, etc but by how much, is it worth taking up marathon running or should I just jog a couple of times a weeks. The analogy with climate change is I know CO2 is heating the atmosphere and I am told we need to reduce by X% by 2020, but all I am told is the catastrophic consequences of doing nothing on CO2 (being obese) rather than what are the trade offs with doing something a bit less X-5% (being on the high side of normal weight).

  9. I’d like a levy food quality-based levy on foods. Staples and combinations of staples that passed muster as adequate in nutritional terms — (i.e. not high in LDLs, or highly concentrated in refined sugars or other highly refined carbohydrates) would be zero-rated and as their proprtion of these rose, the rate at which they were taxed would increase. Again, the funds raised would be hypothecated, going in part to support those dealing with obesity, bariatric care etc and also to sustain locally run quality food coops to which people on below average income would have relatively privielged access. As with the CO2 price, a stored value card would allow people to shop for quality food staples at a discount.

  10. @ChrisB
    Not true.

    Population studies that try to link average life duration and average obesity are confouded by numerous factors, especially medical progress. However, virtually every study that I have seen that correlates body weight with disease prevalence finds a U shaped curve with minimum incidence rates at a BMI of about 22/23. Lower than this you are probably starving yourself or sick; higher and you are hurting yourself. Besides the usual cardiovasular and diabetes these results are common across many cancers, a range of other diseases and aging in general. These results are backed up by physiological evidence of cumulative negative impacts of bloated fat cells on the body.

    There are some considerations that that weaken these results, especially the correlation between BMI and sedentry lifestyle. On the other hand, while BMI is easy to measure, it is an imperfect measure of obesity. Body shapes vary and research is indicating that it’s fat around the gut – aka “male fat” that is the problem more than distributed fat. (Or female fat on the breasts and hip which requires physiological effort to maintain so is a sign of youthful good health.) If a better fat measurements were used the impact of obesity on disease would probably increase.

    None of this stuff is completely rock solid but the indications are pretty plain. The fact that you might now have an increased life expectancy despite being overweight doesn’t mean that much if the extra life is spent in a poor state of health, unable to do much, and kept alive by drugs. I aim to get as close you can reasonably manage to a BMI around 23 while maintaining activity and equanimity. People should take general body shape and fat distribution into account as well as the simple number.

  11. Jim,

    There is an important caveat about what you say – for the over 65’s, higher BMI has a protective effect. Death rates, from pretty much every cause, are lower for those with a BMI over 23 . The most dangerous thing to be as you get older is underweight. Death rates pick up markedly as you head below 20.

  12. @Michael

    Does that exclude those whose low body weight was a consequence of some disease rather than simply their body type?

    One imagines that someone who, for example, developed cancer, and received treatment for it, would probably lose weight before they died. Similarly, someone who was sleeping rough and thus not eating well would be far more likely to get ill and die than someone who was not and one would not suppose that they would have a high BMI at that point.

    On the other hand, we do know that obesity is associated with a great number of life-altering and commonly lethal diseases, so the idea that high BMI could be protective calls for some pretty impressive controlled studies.

    One might also note that not all life years are of equal quality. If one is persistently ill through one kind or another of disease associated with obesity, and persistently unable to enjoy life as one would want it as a consequence of overweight, that we have the technologogy to prolong a ruined life is moot. A person in rude good health who requires few health interventions but who dies suddenly from some cause unrelated to her/his body type two years earlier than someone who almost certainly will die from such a cause has not been worse off.

  13. Great article and shot of the Prof in todays SMH money section page 3 – and Prof you are definitely looking nicely lean. The diet is working – now post it in here!

  14. Jim Birch –
    I don’t think you’ve really answered my points.
    (1) “virtually every study that I have seen that correlates body weight with disease prevalence” – OK, let’s say that’s true. If, then, the all-causes death rate doesn’t show much correlation this would imply that there’s a protective effect of overweightness generally.
    (2) You don’t address the issue of confusion of the data through class. The studies also include
    comments like “the mother’s education (MOMED) has a coefficient of -.161…. a one-unit increase in a mother’s years of education causes a decrease in the respondent’s future BMI by .161.” If, as the Whitehall studies suggest, hierarchy is an independent ill-health factor, and if fat people are poorer and lower in class than thin people, the issue of which is the predominant problem is not concluded.
    (3) “The fact that you might now have an increased life expectancy despite being overweight doesn’t mean that much if the extra life is spent in a poor state of health, unable to do much, and kept alive by drugs.” Well, yes, that would be relevant if the statistics said that while life expectancy was increasing healthy life expectancy wasn’t, but the stats don’t say that. The average period of disability at the end of life is remaining about steady. Again, the effect of obesity isn’t showing up in the stats. – perhaps because, as Michael says, the studies tend to reverse themselves in older people, where most of the deaths are, and perhaps because we’ve all allowed ourselves to be distracted by obesity when the real problem is social stratification.
    Though I will concede that the diagnosis of the problem doesn’t point directly to a remedy.

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