Friday, March 22, 2019 Friday, March 22, 2019

Stephan Guyenet vs Gary Taubes on the Joe Rogan Experience – Post-Debate Podcast

Nutrition is arguably the most emotionally charged of all of the applied sciences. Perhaps it’s not surprising that dialogue surrounding diet is so testy, especially on the Internet.

Why is that? I can think of a couple reasons why it is so contentious.

For one thing, all of us eat, meaning that every single one of us is personally invested in this topic, and we interact with it all the time. We all develop a sense of expertise, in a way that we might not for something a bit more removed from our daily life, like robotics or civil engineering.

In addition, food is arguably the most primal and powerful motivator for animals, ourselves included. And every single one of us has cultivated deep-seated dietary preferences, often established in our formative years. In other words, we are all biased, to varying degrees. It’s hard for us to view our favorite foods in an entirely objective way – even when they are slowly making us sick.

This, of course, is where nutrition science should save the day, right? The scientific method is designed to minimize the influence of bias and help us rigorously understand the natural world. But with modern nutrition, it’s never that simple.

 

FOOD IS NOT THE SAME AS DRUGS

When we study pharmaceutical interventions, we randomly assign participants to one of two groups: either the substance being tested or placebo (or usual standard of care in some cases). With this approach, we can be fairly confident that any difference in outcomes is probably due to the experimental treatment because the groups are otherwise similar. This is the gold standard, with good reason.

In theory, double-blind randomized controlled trials with hard clinical endpoints would also be ideal in nutrition science. But, at the risk of stating the obvious here, such trials are not feasible for addressing the major questions we have related to diet and health. There are obvious ethical and financial limitations, but also problems connected to the behavioral component of diet. For one thing, blinding is difficult (often wholly impossible) in dietary intervention trials. Dropout rates of dietary interventions are very high, much higher than drug trials. Trials to assess weight loss often have dropout rates of 30-40%. And compliance is notoriously low in nutrition interventions, often rendering the results meaningless. Finally, the clinical endpoints associated with diet and nutrition-related diseases like obesity or diabetes take a very long time to develop and require decades of follow up.

This makes nutrition science – and by extension, the science of obesity and metabolism – very complicated. Nutrition science must rely on a mixture of prospective cohort studies, mechanistic studies in humans, animal research, and randomized controlled trials assessing intermediate outcomes or surrogate markers. This demands careful interpretation of a very broad base of evidence, rather than relying on individual studies or single measures of association. Human nutrition is messy, and it’s easy to be led astray or to gravitate to simple solutions. Our guest today knows that all too well.

 

GUEST

In this episode of humanOS, we welcome back Stephan Guyenet. Stephan spent 12 years at the University of Washington researching the neuroscience underlying body fat regulation. You can find more of his excellent work here. Pro users of humanOS will recognize Stephan from the Ideal Weight Program, on which we collaborated. Stephan is also the author of The Hungry Brain – Outsmarting the Instincts That Make Us Overeat.

Most recently, he’s launched RedPenReviews.org, a website where scientists utilize a standardized method to do thorough reviews of popular health-science books.

Stephan has inadvertently become a frequent guest to the show. Long-time listeners may recall previous conversations with Stephan, in which we talked about why we are fatter than our ancestors, whether high-protein diets are actually bad during weight loss, and the safety and effectiveness of ketogenic diets for treating type 2 diabetes.

Earlier this week (as of this writing), Stephan appeared together with journalist Gary Taubes on the Joe Rogan Experience podcast. If you haven’t watched that yet, please go ahead and tune in – it’s a bit long but thoroughly entertaining, perfect for an extended walk on the treadmill. Gary, of course, is best known as the author of the books Good Calories, Bad Calories, Why We Get Fat, and The Case Against Sugar.

This debate was meant to zero in on what causes obesity, and what causes insulin resistance (and the diseases associated with insulin resistance, such as diabetes). These questions have been extensively studied so you would think that the etiology would be well sorted out by now, right? But again, the science of what and how much we eat is fraught with controversy, in a way that is kind of unique to nutrition as a discipline. 

 

WEIGHTY ISSUES

Let’s quickly review these men’s perspectives, and where they disagree:

Gary argues that obesity is a disorder of excess fat accumulation, rather than an outcome of energy balance. He believes that body fatness is dictated mainly by hormones that influence fat storage and fat utilization as fuel. The hormone insulin plays the biggest role in Gary’s model. Gary suggests that carbohydrates raise insulin levels, and elevated insulin effectively shuts down the use of fatty acids as fuel – meaning that you burn less fat and, presumably, become fatter. He also argues that carbohydrate consumption is the cause of insulin resistance.

Broadly speaking, Gary seems to think that both obesity and insulin resistance are relatively simple problems with a single unifying cause (carbohydrate content of the diet), and other factors that have been shown to play a role, like physical activity, caloric intake, and the lipid content of the diet, are not significant contributors.

Stephan has a somewhat more complicated perspective on this. Stephan argues that the primary determinant of body fatness is the brain. The brain regulates appetite, cravings, activity, how much we eat, and other relevant aspects of physiology. We tend to gravitate to energy-dense foods, because such fare would have been associated with greater survival and reproductive success in challenging environments with variable food availability.

But wild animals often share these preferences, yet they seldom struggle with obesity – so why are we so different?

Our environment has changed. As Power and Schulkin aptly put it, in The Evolution of Obesity, “We evolved on the savannahs of Africa; we now live in Candyland.” We have constant access to calorie-dense, hyper-palatable food, which is usually high in both fat and carbohydrates. A doughnut is an excellent example: I know people tend to think of doughnuts as being a carby/sugary treat, but doughnuts are actually relatively high in fat as well. This combination is relatively uncommon in natural foods, and we seem to find it fairly irresistible.

Worse still, we no longer have to engage in physical work to acquire these sorts of foods – in fact, our artificial world virtually discourages physical activity for most of us. Consequently, we are more likely to overeat (particularly if we are genetically susceptible), and we are less likely to expend enough energy to balance out these extra calories. In addition, once we’ve gained weight, alterations in brain circuits that regulate fat mass make it tough to take it off.

So, why have Stephan back on the show this time? Well, despite the duration of the debate (more than 2 and a half hours), a lot of juicy material relevant to this topic didn’t get addressed in the discussion. Prior to the debate, Stephan compiled and posted a list of scholarly references that he planned to draw upon (a handy resource that you should open, if you can, during the debate). But if you take a look, you’ll notice that there’s a good deal there that he didn’t get to. Accordingly, we thought it would be a good idea to have him on the podcast, to address important research that he didn’t get a chance to talk about in the debate, and clarify anything that he felt wasn’t fully elucidated in Tuesday’s discussion. Check out the interview to learn more!

 

LISTEN HERE


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YOUTUBE

TRANSCRIPT

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