Like a large proportion of the world’s population 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, 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).