Stephan Guyenet transcript

Written by Christopher Kelly

June 1, 2017


Christopher:    Hello and welcome to the Nourish Balance Thrive Podcast. My name is Christopher Kelly and today I'm joined by Stephan Guyenet. Hi, Stephan.

Stephan:    Hi, Chris. Congratulations for pronouncing my name correctly.

Christopher:    Do you know what? I've been toiling over that this morning. I'm thinking I'm definitely -- I know I'm going to say Stephan, I'm going to say Stephan. I'm glad we got past that.

Stephan:    [0:00:19] [Indiscernible].

Christopher:    For people that don't know Stephan, he is an amazing researcher that's been very active on a blog for a long time. He earned an undergraduate degree in Biochemistry from the University of Virginia. And then he pursued a PhD in Neuroscience at the University of Washington. He's continued to do research as a post doctoral fellow. He now has a total of 12 years of experience in neuroscience research. And he has been cited by his peers over 1400 times in the literature, which is quite incredible. Stephan, thank you so much for being on today.

    I wanted to start by talking about your new cookbook which I was delighted to see on the website. My wife is a food scientist and she's been working with clients for a few years now and I have to confess that she does all of the cooking in our household. I just do the eating part. Unfortunately, she is away this evening and so I felt like I could probably manage your termites on a stick recipe. And we do have termites. They're eating my house.

Stephan:    Oh, boy. You better eat them up fast then.

Christopher:    Exactly. It's perfect. So, for people that have no idea what we're talking about, I'll link to this in the show notes for this episode. The Bland Food Cookbook. I think it's going to be a New York Times bestseller for sure.

Stephan:    Just to clarify for people. That was in April that it did. But, anyway, it relates to important property of behavior and that is what we eat more when food is more seductive and we eat less when it's less seductive.

Christopher:    And we should get into that in the body of this podcast, I'm sure. I just thought it might be a nice way to warm you up a little bit. So, tell us about the book, The Hungry Brain. I have read the book. I enjoyed it a lot. I would wholeheartedly recommend it to anybody especially people listening to this podcast. I read Robb Wolf's Wired to Eat cookbook, which I also enjoyed. I also read Gary Taubes' new book as well which, admittedly, some of it went over my head a little bit because I listened to it in bed while I had the flu. So, I can't really say I read that but I definitely picked out some bits out of it. And I really, really enjoyed your book. It's very technical. I enjoyed that. I like the technical stuff. Can you talk about why you wrote the book in the first place?

Stephan:    Yeah. I've been doing research on this topic and writing about this topic for the public for a long time on the brain control of the eating. And, I guess, what I've seen is that there's not really a brain-centric perspective in most discussions of eating behavior and body fatness. And that doesn't necessarily mean that a discussion has to be brain-centric to have value but, I think, that eating behavior is generated by the brain.

    So, every aspect of our eating behavior including how much we eat and what we choose to eat is generated by the activity of brain circuits. And so it's obviously a kind of -- It's a pretty obvious way to frame your thinking about eating behavior and body fatness. And also I should mention that body fatness is actually regulated by the brain as well. It's one of the things that the brain regulates either homeostatically or allostatically along with blood pressure and the concentration of various ions and heart rate and many other things in the body, body temperature.

    So, it's kind of an obvious way to frame our thinking but it's not a frame that most people use. And so this is kind of something that I've been trying to remedy through my writing. But when you're writing a blog, it's hard to kind of connect the dots for people because you have these little vignettes that you're writing that people might come by and they might read one, they might read a few. So, they have to be fairly self-contained and that really makes it difficult to construct a larger narrative.

    When you're writing a blog or at least when I'm writing a blog, I'm not putting the same level of effort into it that I would if I were writing a scientific paper or a book or something that was going to be published at a high level just because there's only so many hours in a day and it's difficult to, for something like a blog, to dedicate that kind of time to it. And so I wanted to put something together where I could really take the reader by the hand and lead them step by step through this complex neuroscience of eating behavior and body fatness and do it in a way that was understandable, where it was as understandable as possible where I'm taking complex science but distilling it down to a degree that will be understandable by the general audience.

    And the feedback I received so far indicates that I did that successfully which I'm very happy about. The book is actually about more than just that. It's also about how the brain works. And this is something that I haven't really been hearing people talk about very much with regard to the book. But there's an entire chapter in there that is just about how the brain makes decisions, how the brain decides which action among the millions of possible actions they could take at that particular moment, millions of possible behaviors that could generate how it selects that behavior.


    So, there's all this science in the book about eating behavior and body fatness but also just about how the brain works. That has never really been explained clearly and comprehensively in a general audience book. My wife, when she read this book, she said, called it Stephan's theory of everything. And it kind of is. But it's not my theory. That's the thing that I want to emphasize. It's not really my theory.

    It's me collecting pieces from around the scientific literature and kind of sewing them together in a way that's understandable for a general audience. So, I like to think of it not so much as my theory as the scientific community's theory that I have packaged in this way. But it's packaged in a way that I don't think has been packaged anywhere else. I don't think it's been packaged in this way anywhere else.

    And so that's kind of the rationale for the book. And just to give people a little bit more information on what exactly the book is, it's on the neuroscience of overeating but it's particularly about why we overeat even though none of us want to overeat. So, it's basically a tour of the non-conscious brain circuits that generate eating behavior or push us toward eating behavior even when that eating behavior is not benefiting us. So, either eating unhealthy foods or eating too much food or various types of eating behavior that we know is not really supporting our goals of health and body weight.

Christopher:    Who is the book for? So, this is something that I think that people have run into trouble with in the past, not understanding the context that you're operating in. So, for example, I've interviewed a nephrologist, Jason Fung, who I know you know. He's working with a very particular type of patient. That person maybe morbidly obese, say 400 pounds, they're about to lose a limb to amputation because of type II diabetes, uncontrolled type II diabetes. And so his context is about as serious as it can get. I'm not saying that your work is not relevant to that patient but I would like you to talk about who this book is for.

Stephan:    Yeah. So, I am very ambitious about who I tried to target this book toward. I would like this book to be for just about everyone. I wrote it so that it would be understandable to a general audience but informative to people who are also quite knowledgeable including researchers and physicians. And the feedback I'm getting back so far suggests that I have achieved that objective which I'm very happy about.

    But, I mean, that said, I think it can be useful to a wide variety of people but that doesn't necessarily mean that my book will be able to achieve all goals for all people. So, this scenario that you just laid out of someone who is in deep metabolic trouble and about to lose a limb, I don't think that my book is going to be the first place to go for someone who wants like an actionable plan to not lose a limb. That's not really what my book is about.

    That said, I think that there are insights in the book that could help that person and could particularly help them understand how they got to where they are. But, yeah, in terms of like that practical clinical edge to specific health challenges, I think that is not really what the book is about. I also think that if you're really a hard core researcher looking for really specific detailed information on a particular topic, I don't think my book is really where you're going to find it.

    I mean, my book stays on a fairly high level of analysis of the scientific literature. And there are tons of references for you to go deeper if you want to. But it's not written like a scientific paper. There's not a lot of numbers in it. I don't talk about what statistical tests were applied and whether they were appropriate and really like nitty-gritty stuff like that is not in the book. So, if that's what you're looking for, it's not going to be there.

Christopher:    That's okay. That's not what I was looking for at all, certainly for me personally.

Stephan:    I wrote it for as broad an audience as possible. But, yeah, there are definitely specific applications that it's not going to be optimal for.

Christopher:    And do you think it's a complete description of why people become obese? I enjoy that because I've seen it in practice, that there are other reasons why people may become obese other than overeating. And they could be things like sleep deprivation or inappropriately managing stress. So, it definitely goes beyond what you might think in the title of the book. But do you think it's a complete description of why people might become obese?

Stephan:    I don't want to use the word complete for a couple of reasons. One of them is that I selected factors to focus on and brain circuits to focus that I think a particularly influential of body composition and eating behavior.


    But, I mean, there are a lot of other things I could have written about that I think also are playing roles that maybe current evidence doesn't suggest are quite as influential as the ones I did write about. So, I mean, there are definitely many other things I could have written about that are probably playing a role. The other reason I wouldn't use the word complete is that I just prefer to respect the limits of scientific knowledge and the uncertainty that we still have about the scientific evidence. And I respect the possibility that our conclusions could change in a decade, at least to some degree our conclusions could change even about the things I did write about.

    So, I've done my best to work with the evidence we currently have but there's no way for me to know that some of those conclusions may not change. There's no way for me to know that those conclusions will never change over decades and centuries. So, I wouldn't use the word complete but I've done my best to give an overview of the factors that seem the most important to me.

Christopher:    And that's all you can do. Yeah, of course, you must reserve the right to be proven wrong in the future.

Stephan:    Yeah, exactly.

Christopher:    And do you think that any of the contents of the book are compatible? I know you're familiar with Gary Taubes' work that perhaps refined sugar is the cause of obesity and metabolic derangement. Do you think that any of what you've written about is compatible with Gary Taubes' hypothesis?

Stephan:    I mean, there is aspects that are compatible, sure. I believe that sugar is one of the factors that drive us to overeat. And I talk about that quite a bit in my book. Sugar is a very powerful reward factor. It's something that drives and triggers and reinforces our motivation to eat food and to eat too much food. Also, I partially agree with Taubes that sugar has some negative effects on health that are probably not entirely mediated by its calorie value.

    So, it has metabolic effects that may be over and above just the fact that it makes us overeat. So, there are some aspects where there's concordance there between his view and my view. I think that the thing that I think he overlooks is that it's not just about sugar. Sugar is not the only reason we overeat and it's not the only reason we gain fat. And, I think, this is actually really easy to illustrate in a very intuitive way.

    If I were to put a bowl of plain white granulated sugar in front of somebody, how delicious is that? Would you want to dig in with a spoon and just eat mouthfuls of plain sugar? Nobody wants plain sugar. It's really not that tempting. But once you start mixing that with flavors, once you start mixing it with fat and starch and other things -- I mean, think about like ice cream, I think, is a great example. Think about ice cream and now subtract the sugar. There's no sweetness. How attractive is that?

    It probably would still taste pretty good but it's not going to be nearly as good as if there was sugar in there and you probably wouldn't buy it as much. You probably wouldn't eat it as much. But now, try subtracting the fat. I mean, fat free ice cream is not that good. It tastes kind of good because of the sweetness but, I mean, personally, I wouldn't even think about buying fat free ice cream and I wouldn't eat it unless maybe it was in front of me.

    The point is that the fact that we're willing to eat ice cream at the end of a meal when we've already had a big meal and we're full and we don't need any more calories and we're willing to eat that ice cream or eat that cake or whatever, it's not just about sugar. It's about this confluence of reward factors in that food one of which, an important one of which, is sugar. But there's also fat and starch and the flavors as well as reinforcing drugs in chocolate like theobromine and those things all come together to drive our motivation to eat extra food.

    And it's interesting because in Taubes' latest book he talks about the fact that sugar is a powerful reward factor and I completely agree with that. It's a very motivating thing for humans and many other species. But it's just not the only thing that does that. There are other food properties that do that. There's a bigger picture out there than just sugar.

Christopher:    Right. And this is beautifully illustrated by the potato hack. Maybe you'd like to describe the potato hack. I think you know what I'm talking about.

Stephan:    Yeah, absolutely. And this is another thing I talk about in my book. And by the way, I'm not recommending this. I really can't recommend this for liability reasons. But I do think it's interesting to discuss. There've been many examples of people eating potato only diets. The first one was in, I think, the 1920s or 1930s. And there are these published examples of people eating potatoes for up to a year with almost nothing else except a small amount of fat, very small amount of fat, and they're fine.


    They do just fine. And, in fact, what we've seen recently is that people who carry excess fat have been using these potato diets to lose weight. And it's actually -- And I say lose weight. What I mean is lose fat although some lean mass will also be lost. But the thing that we're interested in here is the fat loss really. That's the key variable that is beneficial. But we're seeing this from the Washington potato commissioner, I forget the guy's name, who went on a -- It was like a three or four month potato only diet and he has his blood parameters checked, his body weight and his blood pressure, basically across the board, everything improved.

    And then we have this new Spud Fit guy who's doing the same thing. I think he's been eating nothing but potatoes and sweet potatoes for almost a year now. And he's having major weight loss. And a lot of other people have tried the same thing with similar results. And it's like, again, I'm not suggesting that we should all go out and do this for weight loss. But I do think that it complexifies, at a minimum it should tell us that the hypothesis that carbohydrate is inherently fattening and less carbohydrate is inherently slimming is not correct. We need a more complex hypothesis if we want to be able to incorporate that information into our understanding of the world.

Christopher:    I interviewed an amazing woman called Ellen Langer who had spent the last four decades doing research on the mind-body connection. And it would seem from her research that it makes no sense to try and separate the two things, that the mind and the body are one. And she's shown through some quite interesting experiments that wonderful things can happen when you put the two things back together.

    So, one example I'm thinking about is the housemate study where a group of housemates had no time to exercise but then they were told that the work that they were doing was, in fact, exercise. And everything else, it was very tightly controlled experiment. They just spontaneously lost weight by just knowing this information. And so something strange that I think that we don't fully understand is going on here. I really recommend that everybody check out Ellen Langer's work. I did a podcast with her that you can maybe start there.

    My conclusion was that it makes no sense to separate mind and body and yet your book seems to exactly that, saying the problem is all in the brain. Would you disagree with that?

Stephan:    I very much agree that -- Of course, if you believe that the brain is a biological machine then, yeah, the mind and the body are one thing. The brain is the information processing organ of the body. So, yeah. And, obviously, they interact in many ways. I think that perspective is perfectly compatible with what I wrote in the book. And here's how I reconcile it.

    So, the book is really a brain-centric view of the process of eating behavior and body fatness. But it's not saying that the brain is like in a jar and not interacting with the body or anything else and just kind of spontaneously generating impulses to eat. The way the brain works in very broad strokes -- And by the way, this is basically the same way a computer works. It receives input through sense organs and through all sorts of input from inside the body.

    It's receiving input from both inside and outside the body. It takes the information from both of those sources and it integrates it and then uses that to generate what it believes are the most appropriate outputs both inside and outside the body. And what happens inside the body we call physiology and what happens outside the body we call behavior. But, basically, the point is that the brain, when it generates eating behavior, it's always listening to what's happening inside the body and to what's happening around you.

    And the signals that it's getting as it listens are a major determinant, probably the main determinant, of what your eating behavior is. And so, signals coming from your fat issue like leptin, signals coming from your digestive track like CCK and GLP-1 and amylin and all these things, food cues in your immediate surroundings, what other people are eating, whether you're seeing ads, what you're smelling, those things are all cues that the brain is taking in and integrating.

    So, the brain is in a dynamic interplay always with not only the body but with everything surrounding the body. And so I don't view -- Even though we can conceptualize of the brain as something separate from the body, I think in real life it's all part of a system that is interacting together to try to promote the survival and reproduction of the organism.


Christopher:     And do you think your model sufficiently describes what happens in bariatric surgery? Because that's really, really interesting the way that bariatric surgery can reverse metabolic derangement in a period of time that seems almost too short for food to be anything to do with it and not even stopping eating would have that great of an effect? Do you think your model is compatible with that?

Stephan:    Oh, yeah, absolutely. I mean, I discussed this a little bit in the book. But, yeah, I mean, so bariatric surgery is really fascinating for a couple of reasons. I'll just explain this for the audience a little bit. By the way, this is not true of all types of bariatric surgery. Only some types have this effect. But the ones that do, such as roux en y gastric bypass and vertical sleeve gastrectomy, they have very profound effects on fat loss and on glucose homeostasis. So, what you see is that bariatric surgery, there's types that I mentioned, is way more effective than any other intervention for promoting fat loss.

    There's no diet, there's no exercise program, there's nothing else that even comes close to what you see with bariatric surgery. I mean, you'll see people who are morbidly obese who lose -- And this is not just anecdotes. This is like the typical response. And they will lose the majority of their excess fat mass and keep it off. I mean, that's like unheard of from diet and lifestyle intervention. So, it's pretty amazing. And when I say that's unheard of, I'm saying you can find anecdotes supporting anything but I'm saying that's unheard of in scientific studies of other diet and lifestyle interventions.

    So, it's just like far and away much more effective. And it has profound effects on food preferences as well. You see that people who undergo bariatric surgery, they lose their affinity for calorie dense fatty sugary foods. And they start gaining a greater appreciation. Their eating behavior starts gravitating towards lower calorie density things like fruits and vegetables. And interestingly, I mean, you might think, well, okay, they had this surgery and now they're highly motivated to make the most of it and so they're making a conscious decision to change their food intake.

    But, actually, you see the same effects in rodents that undergo gastric bypass. So, there's something physiological that's happening that changes food preferences. So, a couple of points. One of them is that we know that food preferences originate in the brain. I mean, all preferences originate in the brain. All behaviors that result from those preferences are an output of brain activity. So, there's clearly something about the surgery that alters how the brain generates eating behavior and how the brain generates food preferences.

    And this is very consistent with what we know about the importance of gut brain communication in regulating food intake behavior and food preferences. As I discuss in my book, there are pathways of communication between the gut and the brain that determine food reward, just the reinforcement and motivational of food as well as satiety. And those things respond to specific nutrients in the small intestinal lumen.

    There are specific receptors that then transmit those signals either by the vagus nerve or other pathways that we haven't identified yet up to the brain, brain stem, nucleus accumbens, you get dopamine, you get other things and you get these reward and satiety outcomes. And that very much depends on the structure and the function -- Those processes very much depend on the structure and the function of the gastrointestinal tract.

    And so we don't know -- By the way, I'm not saying that I know exactly how gastric bypass works in terms of the specific mechanism. But, I mean, in broad strokes, it's very consistent with this idea that the brain is being strongly influenced by signals arising in the gastrointestinal tract that are determining our eating motivation both in terms of our food reward and our visceral hunger level. So, that's one point I want to make.

    I think it's very consistent with what I wrote in my book. I would have loved to cover that in more detail but I didn't because we don't quite know how it works yet. But someday, I would love to write a chapter on that because I think it's really fascinating. But another thing you see that's gotten a lot of attention with gastric bypass is these incredible improvements in glucose homeostasis. You see that people who start off diabetic, most of them experience complete remission of their diabetes and, again, there's not really any other diet or lifestyle intervention that even comes close to that. And naturally people are really, really interested in how this works.


    So, there had been a lot of studies on whether it's just purely due to the fact that they're eating less calories. Because, I mean, especially immediately after the surgery, you're basically fasting. You're almost fasting for a few days.

Christopher:    But it was my understanding that not even fasting works that well. You could take an obese person and get them to fast for that duration of time and you still wouldn't see that improvement that you do with the bariatric surgery.

Stephan:    Yeah, that's actually controversial.

Christopher:    Okay.

Stephan:    Yeah, that's controversial. And I would say that right now -- And, by the way, I'm not suggesting that I have the final answer on this. I'm not really an expert in this area but it is an area of interest for me so I have been following to some extent the research. I'm not 100% up to date on it. But my understanding is that the latest is that the pendulum is swinging toward the field believing that it actually is all about the calories, or at least mostly about the calories.

    Because, actually, when you take subjects and you strictly match their calorie intake that of a person who underwent bariatric surgery, I know that at least some of the studies suggest that it actually does have the same effect on glucose homeostasis. And we actually have other studies independent of bariatric surgery that suggests that very low calorie diets -- I don't know if you've seen that study, the eight weeks on the very low calorie diet causes diabetes remission in a lot of people.

    So, there's definitely a link between hypocaloric diets and improved glucose homeostasis. And this is consistent with the fact that there's a huge amount of evidence suggesting that diabetes risk is very, very sensitive to calorie intake and body fatness, very, very sensitive. Probably the most sensitive of all of the common nutrition related disorders to that. But again, I don't want to suggest that I had the final word. And there may be -- and I know that it remains controversial so I don't want to suggest that it's been settled. The fact that controversy exists suggest that not all the studies have shown exactly the same thing.

    But my impression just from hearing people in the field talk about it recently is that the pendulum is swinging in the direction of calories right now. And I do feel very confident that calories are part of the explanation. But whether they're the full explanation, I don't know.

Christopher:    Let's talk about my favorite section of the book, about dopamine. I really, really enjoyed that section on dopamine. Part of the reason I enjoyed it so much is I've done some research in machine learning recently and I spent most of my time looking at deep convolutional neural networks and identifying objects in photographs for which that type of algorithm is doing really, really well at the moment. And I happened across David Silver's cause on reinforcement learning. I'll link to that in the show notes in case people are more interested.

    But some of the things they're doing with reinforcement learning at the moment is just absolutely amazing. And the thing that's amazing to me about it is it's modeled after what happens inside of your skull with dopamine. So, it's really, really exciting. And understanding how this thing works is just fascinating to me. So, could you talk a little bit about dopamine, the learning chemical?

Stephan:    Yeah, absolutely. So, I think, dopamine is an extremely fascinating molecule. I actually learned a lot about it as I was writing my book. I learned some things that I didn't know previously and the more I learned about it the more amazing it became. One of the reasons why it's so amazing is that it does multiple things in the brain at the same time it performs multiple key actions that intertwine in a very logical and efficient way.

    So, when you hear of dopamine discussed in popular media, usually it's referred to as the pleasure chemical or something like that. And that is a view of dopamine action that has not had any support in the scientific community for like 20 years, the better part of 20 years. It's this thing that kind of got stuck in the popular mind. It never got un-stuck even though science kind of left that behind a long time ago.

    But dopamine really is a teaching signal. It's a reinforcement signal. So, more than anything else, dopamine and particularly in the ventral striatum or nucleus accumbens is the essence of reinforcement. And so, reinforcement is this instinctive, intuitive, non-conscious learning process that sets our motivation and our affinity for certain goals. And so, for example, we learn what foods to prefer over the course of our lives because there are certain nutrients in foods such as carbohydrate and fat and protein that trigger dopamine release in the brain. Your brain says, "Oh, that's cool. Now, I'm going to record all of the sensory information that was association with those nutrients."


    So, for example, the smell or the sight or the taste of pizza. And then the next time I encounter those triggers, those sensory cues, they're going to be triggers that trigger my motivation to obtain and eat that food. So, basically, dopamine trains you to be instinctively intuitively motivated toward goals that previously achieved an objective such as obtaining these nutrients that our brain are hardwired to want.

    And so, basically, what happens is like when you eat, let's say, you eat a slice of pizza -- I like using pizza because I like pizza a lot. It's one of those foods that I don't eat very often but it's one of those things that I have a hard time controlling myself when I'm around it and so I don't put myself around it very often. Pizza for me is like the definition of dopamine.

    But when you eat a piece of pizza, let's say, for the first time, all those nutrients get detected in your small intestine and dopamine starts to spike in your brain. And then, as I said, that increases your affinity for all those cues, the sensory cues. But then the next time you encounter the pizza, what happens is that dopamine kind of skips up the causal chain. Dopamine doesn't spike when you eat the pizza the next time. It spikes when you encounter those cues. So, the next time you encounter the pizza, dopamine starts to spike when you smell it or when you see it instead of when you're actually eating it.

    Basically, it continues to creep up the causal chain until it goes as far as it can to the cues that are most distally associated with that reward. And so, for example, let's say the second time you eat it, it starts to spike when you smell it and taste it. The third time you eat, it starts to spike when you walk into the pizza restaurant. The fourth time, it starts to spike when you drive past the pizza restaurant. And so like, basically, dopamine attaches to the farthest predictive cue that it can that is reliably associated with the availability of that goal. Does that make sense?

Christopher:    It does, yeah. It does.

Stephan:    Interestingly, so dopamine causes you to learn. That's one of the things it does. But the second thing it does is it triggers your motivation. So, whenever that dopamine starts to spike when you encounter that cue, that tells the brain this food or this, whatever it is, is available whether it's gambling or sex or drugs or whatever it is you like. It is available. And when that happens, that triggers your motivation. And dopamine itself is a causal key driver of that motivation.

    So, basically, dopamine causes you to be motivated by the most distal cues that predict the availability of your favorite food or whatever your goal is. So, it both causes you to learn to be motivated and it actually triggers that motivation when you're in the right scenario.

Christopher:    Yeah. That makes sense. There's a very famous Robert Sapolsky lecture that I mentioned with Tommy in an interview yesterday and I should link to it again the show notes because it's so splendid. Robert Sapolsky described this rodent study and the punch line is that nothing is addictive like maybe. They did this experiment. If the rat was not sure if it was going to get a reward, you saw a much greater release of dopamine. It's like the "maybe" bit is really, really addictive.

    And that kind of makes sense when you think about it. If it's not certain you're going to get the goal, then it makes sense to release more of the thing that's going to make you do the action. So, do you think that's compatible with what you found with food reward?

Stephan:    Yeah, that's an interesting question. I've heard about this research but I'm not really familiar with it. So, honestly, I can't comment on that.

Christopher:    Okay. That's fine. But you did describe some rodent studies in the book that talk about nose poking. Can you remember those?

Stephan:    Oh, yeah, absolutely. This is an experiment that's been done a number of labs but that particular setup I describe was done by my friend Ross McDevitt who at that time was a post doc at the National Institute of Drug Abuse in Baltimore. It's an experiment that illustrates the power of dopamine. So, what he did was he took some mice and used a technique called optogenetics where you put a special kind of protein into certain neurons in mice and then that allows you to activate them very precisely using light. They're light activated ion channels, is what they are, if we're going to be technical.

Christopher:    Okay.

Stephan:    So, basically, you put a fiber optic cable into the animal's brain and then with very precise temporal control you can control any neuron population that you want in the brain. And the temporal control is kind of important because neurons fire in specific patterns.


    They don't just kind of turn on for ten seconds and then turn off. They fire in bursts. And so being able to have very precise temporal control allows you to manipulate neurons in a way that's closer to how they would actually fire in real brain. So, the part of the brain that releases dopamine into the ventral striatum or nucleus accumbens in both rats and humans is a part of the brain called the ventral tegmental area, VTA.

    And so what he did was he was stimulating dopamine producing neurons in VTA getting them to produce dopamine in the nucleus accumbens. And this is like -- By the way, just to clarify, I call the nucleus accumbens the ventral striatum in my book. And this is really the essence of motivation, essence of reward, reward being a kind of blanket term for reinforcement and pleasure and motivation.

    So, when you stimulate this, it's very, very powerful in reinforcing in rodents. And so what he did to demonstrate this was he put mice in a cage with this fiber optic cable in their head and in this cage was a little nose poke box. So, it's a little box in the side and every time the mouse sticks its nose into it, it gets a pulse of light going down into its ventral tegmental area that releases a big burst of dopamine into its nucleus accumbens or ventral striatum.

    So, this is like the essence of reward. Like I said in my book, this is like the equivalent of having sex and eating chocolate and getting a raise all at the same time. And what happens is that the mouse will be going around in its cage and the nose poke box is sitting there but it's pretty irrelevant. Like the mouse doesn't really care about the nose poke box originally. It's just walking around its cage exploring everything in there.

    But eventually, by chance, it sticks its nose into the box. And it gets this massive release of dopamine. And that's like, "Whoa, that was amazing. I'm going to do that again." And after it has done it a few times, it realizes how amazing that box is and it starts poking its nose into it constantly. I forget exactly what the rate was that they're sticking their nose in but they're basically doing nothing but sitting there and sticking their nose in this box. And I've seen it. I've been in the room and watched it and they're pretty obsessive about it.

    This shows that this dopamine mediated reinforcement can cause an animal to associate a specific arbitrary cue with a positive rewarding outcome. So, in this case, the nose poke box was completely meaningless at the beginning of the experiment. The mouse had no particular affinity for it. But over the course of the experiment, it developed into a very powerful motivational trigger by virtue of its association with that dopamine release.

    This is how a drug addiction works. Drugs go right to your brain and they increase dopamine release. That is how all drugs work in terms of, I should say that's how drugs of abuse work, the ones that are habit forming. And so either directly or indirectly they increase the activity of that pathway. That's basically very similar to having a fiber in your head that's hijacking your dopamine pathways.

Christopher:    Do you know what you've just described? You've just described social media on a smartphone, right? This is Instagram you're describing.

Stephan:    Well, I completely agree with that. And I think this problem with food that I talk about how it's excessively reinforcing and excessively rewarding, it's not just about food. This is a general property of modern life. This is what happens when technological development and affluence get to a point where we're able to cater to the innate preferences of the human brain more than ever before in human history.

    We can basically give ourselves exactly what our brains want to such an extent that we over motivate ourselves into these distractive behaviors. There's a good book on this called The Distracted Mind about how, basically, humans are intrinsically motivated to be information foragers and that's one of the things, novelty and information is one of the things that presumably spikes dopamine for us since information is so critical to our survival and reproduction as a species. And, basically, the modern conditions of having a smartphone and computer and the internet trigger our information foraging motivations to such an excessive degree that it can become pathological.

Christopher:    Right. That's what I love about the book. You just explained how the world works and once I understand this broad principle, I can then translate it into the things that are going on in my life. And they may be food, they may be other things that I'm finding particularly addictive.


    I really want to go back and look at this more closely now that you said that you're not totally familiar with it. But I think the uncertainty is like a really important thing. You post a picture on Instagram. Did people like it? Didn't they? I need to go back and check, look at the notifications. Do you know what I mean? There's a huge element of uncertainty that's built into these applications.

Stephan:    I think you're right. And again, I'm not an expert in this area. But, I mean, I've always kind of wondered what the appeal of gambling is. Why is gambling so addictive? Personally, I don't get anything out of gambling. But, I mean, a lot of people obviously do to a point where it can literally be addictive.

Christopher:    Right, right, right.

Stephan:    And so why is that? I think maybe it's exactly what you're saying. I mean, obviously, there's the potential for a big reward there. But, I mean, if you really do the utility function calculation, it makes no sense to ever gamble. The odds are, obviously, stacked against you in any casino.

Christopher:    Right. And then the worst the odds, the greater the dopamine, right?

Stephan:    Yeah. And there's something about that uncertainty. There's certain kind of reinforcement schedules where that uncertainty just like, for whatever reason, just titillates the brain in just the right way and sparks that motivation. I think you're right about that. I know there's been some research on it. It's very interesting topic but not something I know a lot about.

Christopher:    Well, we better get into prescription section. So, let me be very precise with my context. I think a lot of people listening to this will be athletes looking to improve their body composition. What should those people be doing? Do we really all need to start cooking only from the Bland Food cookbook?

Stephan:    I think we should all just be eating nothing but potatoes. No, kidding.

Christopher:    Even I can grow potatoes.

Stephan:    So, there are a number of things I talk about in my book. One of them that I think is particularly important is controlling your food environment. So, the brain is very reactive to the cues in your environment. So, if you have foods in your counter particularly highly rewarding foods that are calling to you, they're sending you sensory cues such as the visual and maybe the olfactory cues, those things are going to trigger your motivation to eat them and you're going to have to fight yourself to not eat them.

    So, having food cues around in your personal environment is not going to support your goals when those things are not consistent with what you want to be eating. And also creating little effort barriers for yourself, I think, is really important. The amount that we eat is determined by our motivation to eat but also how much effort eating requires. So, basically, the harder it is to eat the more motivation it takes for you to actually engage in that behavior.

    Like think about how hungry you'd have to be to climb a tree to get a bunch of nuts as opposed to having those nuts right in front of you within arms reach. Or think about how hungry you'd have to be to stalk a kudu on the African savanna for three hours, kill it and then drag the carcass back to your camp. You probably have to be pretty hungry before you're willing to do something like that. So, just even creating very small effort barriers like having nuts in the shells or having oranges in the peel and having the nuts not be salted so they're not quite as tempting to you.

    Doing little things like that, I think, helps to align your energy intake with your true energy needs instead of, and get rid of that eating that's just like, oh, hey, I wanted to eat this because I was bored or because I saw it and it was easy and it was an arms reach. You cut out that unnecessary eating. And for a lot of people, that's going to support improved body composition depending on kind of what level you're already at.

    Another thing that, I think, is really interesting is that -- So, satiety, fullness, that feeling of satiety is, obviously, something that's generated by the brain like all feelings are. But it's generated in response to things that are happening in the gastrointestinal tract. So, when you eat food at a meal, you take in carbohydrate and fat and protein and many other nutrients and many other chemical compounds, those things are detected by your gastrointestinal tract and they're sent up to your brain stem where they're all integrated together as well as with the volume of your food that's detected by stretch receptors in your stomach.

    All that's relayed up to vagus nerve to your brain stem. It's integrated into a signal that determines your feeling of satiety. But it turns out that -- And by the way, satiety is very, very important. I think we all know this intuitively. Hunger and satiety are very important because they determine when most of us terminate our meals.


    So, if you're just sitting down and eating until you feel comfortably full, like most of us do, the point at which you achieve that satiety is going to determine the size of your meal and how many  calories you ate. It turns out that the system is actually not really that tightly connected to the number of calories we eat. So, some food properties trigger more satiety than others per unit calorie.

    So, for example, foods that are lower in calorie density, for example, bowl of oat meal versus crackers, oat meal is much less calorie dense because it has more water and fiber per unit calorie. It's a lot more filling than crackers. That's one factor. The amount of protein is another factor. So, more protein is more filling per calorie. That's been, I think, pretty well established by a pretty large amount of research.

    Another thing that matters is the fiber content. So, higher fiber food will be more satiating per calorie. And then the last factor is the palatability or pleasure value of that food. So, foods that are more palatable are less filling per calorie. Foods that are blander, less palatable, are more filling per calorie. And, I think, this is one of the reasons why the plain potato is so satiating. It's just not very exciting. And it can be exciting if you put cheese and bacon and butter and everything on it. But a plain potato is pretty bland.

    If you think about what kinds of foods our ancestors ate, they're eating unrefined unprocessed foods that had high protein and water and fiber content. These are the types of food that generate a lot of satiety per unit calorie. And also, they were generally simpler foods. They weren't like cooking with herbs and spices and added sugars and fats and all that stuff. They were just kind of like throwing meat on the fire or baking tubers in the fire or eating fruit off the tree and that sort of thing, very simple foods.

    But if we look at the foods that we're eating today that predominate and that we call junk foods that we intuitively understand are fattening, these have the opposite properties. They have a high calorie density, high palatability, usually but not always, low protein and low fiber. So basically, to achieve satiety on those types of food such as pizza, one of my favorites, you have to eat a lot more calories to get to that place of comfort than you do when you're eating whole natural foods.

    That, again, has to do with the way your brain stem is integrating these gastrointestinal signals that are sending from your stomach and your small intestine. That's two things.

Christopher:    That's really, really helpful. The thing I love the most about this is it's simple to prepare. You see all these recipes on the internet -- We all lost weight on the paleo diet because we simplified our diet and now industry has caught up and filled those opportunities. There's all kinds of complex paleo recipes on the internet now. Most of them are completely beyond me. But termites on a stick, I can do, simple food. Cracking your nut with a -- I can do that. So, it's good news all around for me.

    Actually, the first time I interviewed you, and I should link to this interview, I did make some changes then which was to stop buying the salted nuts. That's a really good tip. I didn't feel like I was depriving myself at all when I made that change. We have some normal regular cashews in the kitchen next door and they're not salted. I hardly ever touch them. It's really weird. I didn't feel like I was being deprived of anything but I still don't eat them. I don't eat them anymore. Yeah, it's very strange but so simple and really, really helpful.

Stephan:    Cool. Glad to hear that was useful.

Christopher:    The only thing is, though, I do have a piece of 100% dark chocolate on my desk as we speak recording this interview. Maybe something special about the theobromine that I've realized. Maybe you could just talk about the theobromine really quickly at the end?

Stephan:    Yeah. So, I mean, chocolate is the most craved food among women and it's a very commonly craved food among men as well. It makes perfect sense from the perspective of food reward, and I discuss this in detail on my book. But, basically, if you look at the properties of chocolate, it has all the stuff that the brain wants. It's very, very calorie dense. It's very high in fat. It's typically high in sugar, although yours is not.

Christopher:    Yeah, no. The theobromine does it for me, I think.

Stephan:    And that's the other thing that kind of puts this over the edge. If there was just the sugar and fat, it would taste great but not -- It wouldn't be quite as motivating and not quite as addictive as it is. And that's because of this habit forming drug called theobromine, which is very similar to caffeine. It acts on the same dopamine pathways. I think it acts a little bit downstream of actual dopamine release but it's in the same pathway.


    It acts on adenosine receptors which are -- They dimerize with dopamine receptors and acts on the same pathways in the ventral striatum. And it's not like an amazing drug the same way caffeine is not an amazing drug.

Christopher:    Right. But it's good enough.

Stephan:    Once you add it to these other properties that are already very motivating and very dopamine stimulating, you get something that it just puts us over the top. And, I think, 100% chocolate, unsweetened, which is what you're talking about, is still pretty darn good but it's definitely a step down from sweetened chocolate. You take out that sugar and that major reward factor, at least in my experience, it does make it a lot easier to control intake.

Christopher:    Right. And certainly I witnessed that with my daughter. She'll eat the 100. In fact, she'll steal if she sees it on the counter. At the same time, when we do get some chocolate with sugar in it, she'll say, "Can I have some of the yummy chocolate?" She doesn't want the 100% dark stuff. She wants the yummy chocolate. Well, Stephan, this has been great. The book is The Hungry Brain: Outsmarting the Instincts That Make Us Overeat. I very much enjoyed it.

    I listened to the audible version which was really, really good. I'm slightly regretting that now because I see that there's some illustrations that I've missed. I will link to it in the show notes. Maybe people can make their own decision. And you've re-launched your website which is awesome, I really enjoyed it. The design of it is -- I feel like you're a minimalist person overall. I sense that you live a minimalist lifestyle and your messages in the book is very minimalist. The new website design is very simple and minimal too. Am I right in thinking that?

Stephan:    Yeah, absolutely. I at least aspire to that. I don't always succeed but I aspire to it.

Christopher:    That's brilliant. Is there anything else that you want people to know about?

Stephan:    Yeah. So, an alternative way, in case you don't want to have to spell my name, an alternative way to get to my website is That URL will now take you to my website. And I want to say I agree with what you said about the audible versus the print copy. I mean, the audible copy, all the text is there but I really do think that the print copy is a better experience and the reason has to do primarily with the fact that there's 47 illustrations that are built into the book and I really -- I hired a professional medical illustrator for that. I think they make a really important contribution to the text. I do think that the print copy is a better experience although I totally understand that people have different preferences about how they like to consume media.

Christopher:    Yeah. I mean, for me, it's like I like to be on the move while I'm consuming this stuff and then also in sauna. It's like my other favorite way to consume this type of content. But it was really annoying. I knew that I'd really enjoyed the section on dopamine and I wanted to read that again and it's not easy on audible. You don't even know where that is in the book. You have to kind of scrub around a bit to try and find it. Yeah, absolutely, I'm going to buy the Kindle version so that I can have it for future reference. And then also I can keyword search inside of it as well. It's super handy.

Stephan:    Yeah, yeah.

Christopher:    Awesome. Well, this has been fantastic, Stephan. Thank you very much. I really appreciate you.

Stephan:    Okay. Thank you, Chris.

Christopher:    Cheers.

[0:53:21]    End of Audio

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