Diets, the evidence and the media: we need a better solution to obesity

Dylan MackayTwo of the most well-known American food journalists have been telling readers lately that the DASH and Mediterranean diets are not tops for our health. But hang on—the evidence tells a different story.The journalists are Gary Taubes, the author of The Case Against Sugar, and Nina Teicholz, the author of the bestselling, The Big Fat Surprise. In their recent LA Times Op-Ed, they accuse the U.S. News and World Report of presenting the failed nutritional status quo in their January cover story on "best diets,” where the DASH diet (short for “Dietary Approaches to Stop Hypertension”) and the Mediterranean diet are tied as best diets overall.Both the DASH and Mediterranean diets promote the consumption of vegetables, fruits and whole grains, and both diets recommend lower intakes of red meat and saturated fat. In the realm of human nutritional sciences, both of these diets are two of the most well-respected. Which is why they ended up on the top of U.S. News and World Report list, based on clear criteria, which was published.Yet, ironically, one of the first claims from Teicholz and Taubes is that both diets do not have enough evidence showing they reduce overall mortality, and they dismiss supporting studies of these diets as being flawed. They also assert that dietary guidelines around the world, which largely have promoted dietary patterns similar to DASH or Mediterranean diets, are responsible for our current epidemic of obesity and its comorbidity, type 2 diabetes.What do they propose instead?Teicholz and Taubes propose a diet lower in carbohydrates (including sugar) and higher in fat, such as “Atkins," "paleo," "ketogenic" or "South Beach"—all of which were ranked low on the U.S. News’ ranking. They explain how these low-carb high-fat (LCHF) diets are well-researched and the answer to our current worldwide obesity crisis.It seems a nice and tidy story, except it isn’t. They are saying the emperor has no clothes, when they are also naked.Unfortunately, good evidence for reduced total mortality on LCHF diets does not exist—it also does not exist for DASH or Mediterranean diets either. But DASH and Mediterranean diets do at least have larger (n>500 participant) randomized controlled trials, something which LCHF diets do not.In terms of weight loss, sticking to a diet that leads to a negative energy balance (eat less than what you burn) is what works, regardless of the diet style. Markers of health, including blood sugar and blood lipids, tend to improve during weight loss irrespective of diet—and as long as the weight loss and diet lasts.In fact, the whole concept of ranking weight-loss diets is a distraction. Any lifestyle pattern that excludes smoking, includes physical activity and leads to weight loss in someone who has obesity (or prevents weight gain in non-obese people) will significantly decrease chronic disease risk, even for those with a genetic predisposition.Teicholz and Taubes also proclaim LCHF as the way to reverse type 2 diabetes, citing an ongoing study as their evidence. While LCHF diets may indeed be able to reverse type 2 diabetes, it is possibly a product of weight loss. This is supported by the Diabetes Remission Clinical Trial (DiRECT), which recently demonstrated remission of type 2 diabetes without the need of LCHF diets.Our dietary patterns, in the macronutrient sense (carbohydrates, protein and fat intake), are more likely the passengers than the drivers of the current obesity crisis.Teicholz and Taubes list the cause of our obesity problem but mis-identify it. They say that people have been following dietary guidelines (Narrator: They have not). Yes, Americans have been “notably increasing their consumption of grains, vegetables and fruits and eating less whole milk, butter, meat and eggs,” as Teicholz and Taubes claim. But what they didn’t note is that Americans have been increasing their total energy consumption overall.We consume more energy than we did in the 1970s. Factors such as urbanization, decreased physical activity at work and at home, and lower food costs (especially for calorie-dense, nutrient poor foods) have all worked together to increase the availability of food energy and decrease its expenditure. These are the real drivers of our obesity crisis, not simply carbohydrate (or indeed, sugar) intake.In this post-fact world, narrative and belief seem to be the only true currencies. In human nutritional sciences, there seems to be a narrative for every diet, and for each diet, an army of believers.Teicholz and Taubes want you to believe that the LCHF diets were not ranked highly because the U.S. News expert panel may have been “entrenched in their opinions, supported by the industries that benefit from these diets, motivated by non-nutrition agendas such as animal-rights activism.” This a strong assertion to level at a panel of 25 diverse and well-established scientists. The accusations of personal bias also seem hypocritical when the authors themselves make some of their living promoting low-carbohydrate diets.In the midst of a worldwide obesity and diabetes crisis, we don't need more input from industries or from people selling books. We need more large-scale, public health interventions that address root causes of the obesity epidemic. It’s time to let evidence dominate the diet discussion.Dylan MacKay, PhD, is an assistant professor in the Department of Community Health Sciences and a Clinical Trialist at the George and Fay Yee Centre for Healthcare Innovation at the University of Manitoba in Winnipeg and an expert adviser with EvidenceNetwork.ca.Opinions expressed in this article are those of the writer, and do not necessarily reflect those of CanadianHealthcareNetwork.ca or its parent company.

Diets, the evidence and the media: we need a better solution to obesity

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