Some of you will be familiar with Gary Taubes’ book The Diet Delusion (entitled Good Calories, Bad Calories in the USA). In this book, I think Taubes does a good job of presenting obesity as not a problem to do with gluttony and lack of exercise, but a problem of fat storage. He argues, quite convincingly I think, that if we want to stem the tide of overweight and obesity, we need to eat less foods that promote fatty deposition in the body. And seeing as the fat storage hormone in the body is insulin, this means eating a diet low in certain carbs. Don’t let this super-condensed version of Taubes’ book put you off reading the whole thing – it’s well worth a read if your interested not in the rhetoric that ‘healthy’ eating messages are awash with, but what the science shows.

Another of Taubes’ ideas is that obesity is hormonally driven. He uses childhood and adolescent growth spurts as a sort of analogy. Here’s his thinking: kids and adolescents can go through growth spurts during which they eat voraciously. The huge volumes of food these kids can pack away are not necessarily due to gluttony, right? Right – they’re due to hormonal signals in the body that stimulate appetite. Taubes quite legitimately asks, if vertical growth can make us hungry as a result of hormonal signals, why can’t it be the same for horizontal growth?

In Taubes’ mind, it could well be that as we put on weight, hormonal changes enhance the appetite which can cause ‘overeating’ and therefore more weight, and so the cycle repeats. This seems utterly plausible to me. Though the mere mention of this concept can, I’ve noticed, not sit too comfortably with those who have been brainwashed into believing that all overweight people must be eating too much or exercising too little as a result of their lack of self control/weak will/inadequate personality or whatever.

I came across a study recently which appears to support Taubes’ theory. I’ll say up front it was done in rats. I prefer generally to stick to human research on this site, but do make exceptions when I feel there is something genuinely interesting to learn from work done in animals.

In this study, scientists focused on two sorts of rat: lean ones and rats bred to be fat (especially around the middle) – known as ‘Zucker’ rats. The scientists found evidence that the fat found in both these types of rats produced a substance called ‘neuropeptide Y’ (NPY). This substance, among other things, stimulates appetite. It was previously thought to originate only in the brain, so finding that it can be made by fat cells too is quite a step forward in our understanding of this substance.

So, in short, fats cells themselves appear to have the ability to produce hormones that stimulate the appetite. What is more, this research found that in the fat (Zucker) rats, NPY levels were significantly higher than those in the lean rats. The authors of this study suggest that abdominal obesity may cause rises in NPY levels which may cause overeating and therefore more abdominal obesity and so on and so forth. I’m sure you won’t need me to point out that this research seems to provide support for Taubes’ notion that that just as vertical growth can be hormonally driven, horizontal growth can be too.

References:

Yang K, et al. Neuropeptide Y is produced in visceral adipose tissue and promotes proliferation of adipocye precursor cells via the Y1 receptor. The FASEB Journal [Epub before print 7 March 2008]

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