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For those interested in the cause of obesity, a lengthy post by blogger and neurobiologist Stephan Guyenet is rocketing around the Internet. After a rather testy exchange with Gary Taubes at the Ancestral Health Symposium (which culminated with Taubes offering Guyenet this no-so-friendly advice: “I would just recommend in the future you should pay attention to populations that might refute your hypothesis rather than just presenting populations that support. That’s always key in science.“), Guyenet decided to write a detailed dissection of Taubes’s carbohydrate theory of obesity, explaining why it’s “not only incorrect on a number of levels, but may even be backward.”
Here’s Taubes’s own statement of the theory in question, as quoted by Guyenet from Good Calories, Bad Calories:
This alternative hypothesis of obesity constitutes three distinct propositions. First, as I’ve said, is the basic proposition that obesity is caused by a regulatory defect in fat metabolism, and so a defect in the distribution of energy rather than an imbalance of energy intake and expenditure. The second is that insulin plays a primary role in this fattening process, and the compensatory behaviors of hunger and lethargy. The third is that carbohydrates, and particularly refined carbohydrates– and perhaps the fructose content as well, and thus perhaps the amount of sugars consumed– are the prime suspects in the chronic elevation of insulin; hence, they are the ultimate cause of common obesity.
Guyenet’s post is an interesting read, and it certainly raises some questions about Taubes’s reductionist approach to obesity (which I’ve criticized in previous posts). It should be noted that Guyenet himself has a Grand Theory of Obesity, which he dubs the “food reward” theory. It basically argues that modern foods trigger reward behaviour in our brains without the accompanying satiety signals that traditional foods would offer. To his credit, he’s more circumspect about trumpeting the powers of his theory: the post I linked to is titled “Food Reward: a Dominant Factor in Obesity.” No doubt that Taubes would have said “the Dominant Factor…” 🙂
Still, my overriding sense is that scientists (and journalists, for that matter) with Grand Theories rapidly become unable to critically evaluate data that conflicts with their theory. Personally, I think it’s highly unlikely that we’ll find a single dominant factor that explains the dramatic rise in obesity over the last few decades, and the endless search for that one magic bullet distracts us from the obvious contributing factors that we already know about.