Gary Taubes on Obesity and Bad Science
Gary Taubes recently wrote an essay about the causes of modern obesity. In it, he correctly points out that modern medical science is woefully ignorant of the true causes of obesity. I haven’t yet read Taubes’s book, and I’m not particularly convinced of his carbohydrate hypothesis (which I’ll address shortly), but I wanted to comment on some excellent words on the practice of science as it’s often used in the human sciences (including both medicine and social science):
Another problem endemic to obesity and nutrition research since the second world war has been the assumption that poorly controlled experiments and observational studies are sufficient basis on which to form beliefs and promulgate public health guidelines. This is rationalised by the fact that it’s exceedingly difficult (and inordinately expensive) to do better science when dealing with humans and long term chronic diseases. This may be true, but it doesn’t negate the fact the evidence generated from this research is inherently incapable of establishing reliable knowledge.
The shortcomings of observational studies are obvious and should not be controversial. These studies, regardless of their size or number, only indicate associations—providing hypothesis generating data—not causal relations. These hypotheses then have to be rigorously tested. This is the core of the scientific process. Without rigorous experimental tests, we know nothing meaningful about the cause of the disease states we’re studying or about the therapies that might work to ameliorate them. All
we have are speculations.
As for the experimental trials, these too have been flawed. Most conspicuous is the failure to control variables, particularly in free-living trials. Researchers counsel participants to eat diets of different macronutrient composition—a low fat, a low carbohydrate, and a Mediterranean diet, for instance—and then send them off about their lives to do so.
Rather than acknowledge that these trials are incapable of answering the question of what causes obesity (assumed to be obvious, in any case), this research is still treated as relevant, at least, to the question of what diet works best to resolve it—and that in turn as relevant to the causality question.
What can we do about this? It seems we have two choices. We can continue to examine and debate the past, or we can look forward and start anew.
We believe that ultimately three conditions are necessary to make progress in the struggle against obesity and its related chronic diseases—type 2 diabetes, most notably. First is the acceptance of the existence of an alternative hypothesis of obesity, or even multiple alternative hypotheses, with the understanding that these, too, adhere to the laws of physics and must be tested rigorously.
Second is a refusal to accept substandard science as sufficient to establish reliable knowledge, let alone for public health guidelines. When the results of studies are published, the authors must be brutally honest about the possible shortcomings and all reasonable alternative explanations for what they observed. “If science is to progress,” as the Nobel prize winning physicist Richard Feynman said half a century ago, “what we need is the ability to experiment, honesty in reporting results—the results must be reported without somebody saying what they would like the results to have been—and finally—an important thing—the intelligence to interpret the results. An important point about this intelligence is that it should not be sure ahead of time what must be.”
Finally, if the best we’ve done so far isn’t good enough—if uncontrolled experiments and observational studies are unreliable, which should be undeniable—then we have to find the willingness and the resources to do better.
I almost couldn’t say it better myself. 😉
In general, medical wisdom in general, particular when it comes to diet, exercise, obesity, and health related to such is based on generally bad science. This has been a general theme of my posts on the matter, and indeed, one of the overall themes of my blog, at least with respect to human differences. These are points I’ve made when discussing this topic, and Taubes pretty much speaks to my thoughts on the matter.
Of course, the very standard that Taubes wishes to hold hypotheses on the causes of obesity to apply to his own hypothesis, namely, that it is excessive carbohydrate consumption per se that is leading surging obesity rates. I’m not sure that that is the case, and this hypothesis needs to be examined with research conducted to the same standard Taubes holds the prevailing wisdom.
And, with all that said, Taubes seems to glance over a very powerful point he raised in his essay:
In these trials, carbohydrate restricted diets almost invariably show significantly better short term weight loss, despite allowing participants to eat as much as they want and being compared with calorie restricted diets that also reduce the quantity of carbohydrates consumed and improve the quality. In these trials, the ad libitum carbohydrate restricted diets have also improved heart disease and diabetes risk factors better than the diets to which they’ve been compared. But after a year or two, the results converge towards non-significance, while attempts to quantify what participants actually eat consistently conclude that there is little long term compliance with any of the diets.
Let’s say that Taubes is correct, and it is excessive carbohydrate consumption that is leading the obesity rate. What do you do about it? Simply suggesting that people go on low-carb diets isn’t going to work because most people cannot adhere to such a diet.
But, theoretically, if we did definitely identify carbohydrates as the problem, massive government intervention in the food market might be able to address this. Through taxes and subsidies, perhaps we could make “fattening” foods considerably expensive, discouraging their consumption. I’m not going to comment of the feasibility of such a plan, but Taubes is certainly correct that we need more and better research into this whole topic.