The Diet Delusion [ pp 601] (published in the USA as Good Calories, Bad Calories) Gary Taubes 2008 There is no topic more widely discussed than what one should eat in order to stay healthy. And there are few topics where the evidence is so lacking in quality. It is also a topic that is besieged by gurus, cranks and supplement hucksters. You need to beware of misleading titles. Dietitians are good. Nutritionists are sometimes good. But titles like ‘nutritional therapist’ and ‘nutritional medicine’ are usually warning signs of alternative therapists and/or pill salespeople. Gary Taubes is a journalist, but he is quite an exceptional journalist. His account of the importance of randomisation for the establishment of causality is one of the best ever and it was published not in an academic journal, but in the New York Times [1]. His book, The Diet Delusion, is in the same mould. It is more complete and more scholarly than most professional scientists could manage. Not only does it cover the literature right back to Samuel Johnson, but it is also particularly good at unravelling what one might call the politics of science. And by politics I don’t mean the vast lobbying industry that has built up with the aim of selling you unnecessary supplements, but the politics of academia. Obesity sounds simple. If you are fat it is because you eat too much or exercise too little, right? Well no, it’s not as simple as that. For a start, it has been shown time and time again that low fat diets, and exercise, have small and temporary effects on weight. The problem with diet and health revolves round causality. The law of conservation of energy is an inevitable truth, but says nothing about causality. It could imply that you get fat because you eat too much, or equally the causal arrow could point the other way and “we eat more, move less and have less energy to expend because we are metabolically or hormonally driven to get fat”. The assumption that positive caloric balance is the cause of weight gain has predominated since the 1970s and “this simple misconception has led to a century of misguided obesity research”. At the heart of the problem is the paucity of randomised trials, which are the only way to establish causality. Those that there are have usually shown that diet does not matter as much as we are told. Taubes concludes “It does little good to continue basing public health recommendations and dietary advice on association studies (the Framingham Heart study and the Nurses Health Study are prominent examples) that are incapable of reliably establishing cause and effect.” I think it can certainly be argued that the problem of causality has been greatly underestimated. We are warned constantly of the dangers of processed meat, on the basis of very unconvincing evidence [2]. This is one reason why we still know so little about the causes of obesity, diabetes and heart disease. For Taubes, a major villain was the US nutritionist Ancel Keys (1904 – 2004). His

forceful advocacy of the low-fat hypothesis in the early 1970s, was, says Taubes, based on ignoring the many studies that did not agree with the idea. It seems that the sort of citation

bias, recently described systematically by Greenberg [3], resulted in great exaggeration of the strength of the evidence. It is quite possible that there was rather more to be said for the Atkins diet than was apparent at the time. The fact that Atkins was not a university scientist, that his views were extreme and that he was so obviously out to make a lot of money from it, gave him all the appearance of being yet another profiteering diet guru. He was dismissed by the medical establishment as a quack. Taubes points out that conflict of interest cuts both ways. Atkins’ sternest critics at Harvard were funded by General Foods, Coca-Cola and the sugar industry. It adds up to a sorry story of a conflict of vested interests and scientific vanity. Taubes’ final judgement is harsh. He quotes Robert Merton’s description [4] of what science is, or should be. “The organization of science operates as a system of institutionalized vigilance, involving competitive cooperation”

In such a system, scientists are at the ready to pick apart .and assess each new claim to knowledge. This unending exchange of critical appraisal, of praise and punishment, is developed in science to a degree that makes the monitoring of children’s behavior by their parents seem little more than child’s play". He then comments “The institutionalized vigilance, “this unending exchange of critical judgment”, is nowhere to be found in the study of nutrition, chronic disease, and obesity, and it hasn’t been for decades.” It took Taubes five years to write this book, and he has nothing to sell apart from his ideas. No wonder it is so much better than a scientist can produce. Such is the corruption of science by the cult of managerialism that no university would allow you to spend five years on a book [5]. I find all ten points in his summary convincing. But his most important conclusion is that you cannot have any certainty without randomised trials. The business of nutrition is greatly at fault for not having put more effort into organising randomised trials. Until they are done, we’ll never really know, and we shouldn’t pretend that we do. 1. Taubes G. Do we really know what makes us healthy? New York Times 2007 Sep 16. [full text link] [pdf file] 2. Colquhoun, D. (3 May 2009) Diet and health. What can you believe: or does bacon kill you?. 3. Greenberg, S.A.. 2009 How citation distortions create unfounded authority: analysis of a citation network. BMJ ;339:b2680 [pdf file]. 4. Merton, R. K. Behavior Patterns of Scientists . Leonardo, Vol.3 1970; 3(2):213-220. From Jstor [or pdf file] 5. Lawrence PA. The mismeasurement of science. Curr Biol 2007; 17(15):R583-R585.PM:17686424 [pdf file] [commentary]