Stephan Guyenet transcript

Written by Christopher Kelly

Nov. 27, 2014


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

    Stephan is an obesity researcher, neurobiologist and author. He has an undergraduate degree in biochemistry from the University of Virginia and a Ph.D. in neurobiology from the University of Washington. His blog "Whole Health Source" is a free resource for anyone that loves the science of health. I would highly recommend it. So after you're done listening to this, go over and have a good read of his blog.

    I wanted to start by asking you about different models of obesity. I should probably give you a little bit of background information. I first stumbled across Gary Taubes' and Peter Attia's work on insulin as a possible regulator of fat burning some time ago and got enormous benefit in my own personal health and athletic performance from following their advice to cut back on carbohydrates.

    Recently, I saw your presentation at AHS -- I was actually there -- and it made me realize that -- well, I guess I already knew that there was much more going on than just that one piece, but it seems like you're presenting a completely different model of obesity. Is that true? Can you explain more?

Stephan:    Yeah. So you're talking about my talk this last year at AHS 14?

Christopher:    Exactly. Yeah, I was there. So the leptin resistance.

Stephan:    Yeah, right. Okay. So yes, it is a completely different model, and I want to start off by saying that on a purely theoretical basis, it's not mutually exclusive at all with the insulin hypothesis that Gary Taubes and others advocate. I believe that the insulin hypothesis or the development of obesity is incorrect independently of whether or not this other model is correct.

    So the other model is the leptin resistance model. I'm actually preparing an article on this right now. There are many different models for the development of obesity and most of them are probably correct to some extent. Obesity is a multifactorial condition, I think that's pretty clear, and so there are valuable contributions that are coming from a variety of related areas of research.

    But one thing that is characteristic of obesity is that it's not just a passive accumulation of fat tissue. There is a system in the body and in the brain that regulates fat mass and that system is actively defending an elevated level of body fat in the situation of obesity. So if you take an obese person and you calorie-restrict them to cause them to lose weight down to the level of body weight of an overweight person, someone who's simply moderately overweight, they are not the same as a person who started off overweight and who has never attempted to diet. Physiologically, metabolically, neurobiologically, those two different scenarios are distinct.

    So a person who is weight-reduced who was formerly obese, their brain essentially activates a coordinated suite of responses designed to restore that body fat that they lost. So their brain is essentially defending that formerly elevated level of fat mass. That's something that my mentor, Mike Schwartz, at the University of Washington -- who's an obesity researcher -- and myself really try to point out to the scientific community is there are probably many things that contribute to obesity but one key characteristic is that this system that normally regulates body fatness and normally would constrain body fatness, something has changed about it.

    So it's really, really important to understand what has changed about it because you can look at overfeeding studies, a lot of people will not gain fat during conditions of overfeeding. Many people will not gain much fat. Many people, if you overfeed them by an excess of 50% of their normal daily calorie intake, they will hardly gain any fat. They have an energy-regulating system that is resistant to fat gain. It simply burns off the excess. So we know that this system has the capacity to prevent fat gain even in the face of massive overfeeding, or substantial overfeeding, I should say.


Christopher:    Does that mean we're doomed to put it back on then? Will that always take place then if the body's trying to defend this set point?

Stephan:    Pardon, can you repeat the question, please?

Christopher:    So are we doomed to always regain any weight that we lose?

Stephan:    Well, I will get to that. Let me finish what I'm saying here and then I will address that question. Okay, so I'm taking a kind of meandering path around this but I think it's pretty important to explain some of this to understand where I'm going.

    So you have this energy-regulating system and it turns out that not only is it re-regulated in obesity but that that is probably a very, very important component of the ability to be obese and to become obese. So it's a very important question. How does this energy-regulating system change in such a manner that it's defending an obese state instead of defending a lean state like it does in a lean person? So most lean people, if you overfeed them, they will activate some of these responses that attempt to resist fat gain, just like an obese person will resist fat loss.

    So it really operates in both directions, and this system consists of a so-called negative feedback loop that's very similar to the one that operates -- or similar in some ways to the one that operates in your home thermostat. Your home thermostat measures the temperature of your house using a thermometer, and then it adjusts that temperature using heat and cooling and it attempts to adjust that back to the preset temperature.

    So the analogy is that part of your brain called the hypothalamus measures the level of body fat in your body using a hormone leptin that's secreted by body fat in proportion to its size, and it uses that measurement to adjust body fat size using a variety of mechanisms toward its preferred value. So it's similar negative feedback system to your home thermostat.

    My talk at AHS 14 was all about how the system works and how and why its function is altered in obesity. That's a very, very important question. I mean, essentially, virtually all of the research we have on obesity suggest that the brain is the major player. So if you look at the genetics of obesity, the genetic variance that modify body fatness are virtually all in the brain, virtually all in the hypothalamus.

    If you look at the genes that when they're mutated produce obesity in humans and mice, they're all in the leptin signaling pathway. I mean, this is the body fat regulating pathway. By far, everyone agrees this the most important pathway of body fat regulation in humans. So understanding how it's altered in obesity is obviously a high priority.

    So essentially, what happens is the brains of obese people become resistant to this hormone leptin just like their tissues become resistant to insulin. They can't hear it as well so it takes more body fat and therefore more leptin for the brain to think a person's not starving.

    So now, we're coming back around to answer the question about how this relates to insulin. Well, it turns out that leptin is not the only signal that the hypothalamus is listening to to determine what your body's energy status is. It's also listening to insulin and it's also listening to a variety of other circulating factors as well as nerve signals that are coming from all different parts of the body.

    So it integrates all this information into a picture of overall energy status in your body that determines whether you should be seeking more food or whether you should be avoiding seeking more food, and that sets your level of hunger, your level of interest in food, how much energy you have for physical activity, how much energy your brown fats bring, your thyroid hormone levels, sympathetic nervous system, everything you can imagine, your immune system function, reproductive function, everything related to the energy availability of your body.


    So insulin is acting in a very similar manner to leptin in the hypothalamus. It's just not quite as influential as leptin but it's doing the same thing, having the same negative feedback.

    So basically, the problem is you get leptin resistance in the hypothalamus while you also get insulin resistance in the hypothalamus. The hypothalamus can't respond as well to that insulin, and now when you get leptin and insulin resistance in the hypothalamus, insulin levels are going up in the circulation. So your insulin is getting higher and higher as a symptom of that insulin resistance. So what I believe has happened is that this insulin hypothesis has confused association with causation and said, "Okay, well, this high insulin is causing obesity," but really, the high insulin is a symptom of the insulin and leptin resistance that themselves are contributing to obesity.

Christopher:    Okay, yeah. So I've seen that. I read about it on your website and it's not the only place I've heard it that as fat cells get larger in size and take on more fat, they also become less sensitive to insulin.

Stephan:    Yeah, absolutely. The elevated level of insulin that obese people have that's supposedly locking their fat away, if you actually look at what their fat cells are doing, the fat's not locked inside and it's getting out just fine. In fact, it's getting out at a higher rate than it does in lean people.

    So there's no insulin or anything else that's locking away fatty acids in fat cells in obese people. Insulin is higher but because of the insulin resistance, it's not exerting a heightened biological effect on fatty acid trafficking as far as the evidence we currently have. So to me, that suggests that the elevated insulin is not really -- well, its simply not packing fat away inside fat cells as has been claimed, because we can measure it and it's just not doing that.

Christopher:    I've seen other tests that look at the amount of fat oxidation and it goes down really sharply with the presence of insulin, right? So this is more important to me. As an athlete, we have lots of fat stored, and if I want to do a long bike ride, I only have so much glycogen and keeping insulin low allows me to gain access to the fat. That's what I've seen from a practical standpoint and I've seen data that supports that.

Stephan:    Oh, yeah, absolutely. Absolutely. So I want to preface this by saying that I'm not really an exercise physiologist. I'm not an expert in physical performance. I know that there's been some debate and some talk about whether fat oxidation or carbohydrate oxidation is preferable for endurance activities. I don't have any answers or even really opinions about whether that's true or not.

    However, what I will say is that insulin does reduce fat oxidation. That's absolutely true. The reason it does that is because insulin is an energy traffic cop. So post-meal insulin, the function of it in large part -- well, basically, the function of it is to coordinate the metabolic shift to burning carbohydrate when you've eaten carbohydrate.

    So essentially, insulin is a signal that tells your body to burn the fuel that you just ingested. So if you eat a meal that's mostly fat, there's little insulin release and your body goes on burning fat, and that doesn't really have any implications for the amount of body fat you're storing because you're not just burning fat, you also are eating fat. So it's the balance going in and out.

    But when you eat a meal that has little fat and a lot of carbohydrate, your fat oxidation goes way down as your body is dealing with that carbohydrate, as your body is switching to oxidize that carbohydrate, and that's just part of the system in our bodies that give us the flexibility to use any fuel that we put into our mouths.

    So if you were to eat a high-carb meal and you were to continue burning fat, that wouldn't really make a whole lot of sense from a physiological standpoint because what would your body do with the carb? Our storage sites for carbohydrate are pretty limited. So there's this metabolic hierarchy where the things that store the most poorly in the body or the things that we have the least storage capacity for are preferentially dealt with.


    So alcohol gets burned first because we can't store it at all, amino acids/protein gets burned second because we have a very limited storage capacity for that, carbohydrate is third because we have a moderate storage capacity, and fat is oxidized dead last because we have an almost unlimited storage capacity for it. I mean, even someone lean like myself, I could not eat any food for probably an entire month and survive based primarily on the vast amount of energy stored in my relatively modest-sized fat stores. So we have a tremendous reservoir for it especially if you consider that our fat stores can expand in an almost unlimited fashion.

Christopher:    I see. So you said something really important there about maintaining body weight. I was a bit rude interrupting you there, but -- so someone that loses weight, are they doomed to always put it back on?

Stephan:    Yeah, that's a really good question, and I don't want to say that I have all the answers to that question but I will give you some informed speculation.

    So if you were to ask one of the world's leading experts on this, perhaps the world's leading expert -- his name is Rudy Leibel; he works with Michael Rosenbaum who's also a leading expert in this -- they study these physiological, metabolic and neurobiological reactions to fat loss. They do these studies where they weight-reduce obese people and they weight-reduce lean people and they show that no matter what your starting weight is, people activate this coordinated starvation response when the fat starts going away and that that depends on a reduction in leptin.

    And then a question -- and a very important question -- is does this start going away after a while? Is this a permanent reaction? Is the body always going to resist fat loss? Or is the body eventually going to get used to it and say, "Okay, well, this is the new way that we're going to start defending"?

    Well, they have kept a limited number of people on this weight-reduced regimen for up to, I think, five years, if I recall correctly, and they report that it never goes away. So these people never stop trying to regain that weight. The brain continues to try to regain the weight. Now, as far as I know, that would be Dr. Leibel's answer to that question. That's what he said the last time I heard him address it.

    However, my perspective is a little bit different because essentially there's quite a bit of evidence in the scientific literature that diet quality can greatly influence the level of body fatness, that person "defense" against weight loss or weight gain. So if you put animals or humans in a situation where the food quality is very calorie-dense, it's refined, it's highly palatable, they will, without intentionally overeating, overeat tremendously and experience increased body weight, and that will be their new plateau that they're defending.

    Conversely, if you put people on a lower-calorie density, simpler, less highly palatable, unrefined type of diet, people or animals -- there's more research on this in animals than people -- they will begin to defend a lower weight, and what I mean by that is their spontaneous calorie intake will go down, their body weight will go down, but they'll still be eating to fullness. They're not hungry or they're not starving. They're eating as much as they want to eat but their body weight is lower, and if you try to then perturb their body weight by underfeeding or overfeeding, you will realize that they are defending that new body weight plateau against changes.


    So for whatever reason, diet quality can affect the defended level of body weight. There's a fairly good amount of evidence to support that.

Christopher:     So it sounds like for two reasons then. It's crucial that if you do lose weight, however you do it, it must be sustainable because if you stop doing it, then it seems almost certain that you'll regain the weight.

Stephan:    Yeah, that's absolutely true, and there's a tremendous amount of evidence to support that. If you look at almost any weight loss study, weight regain is the rule rather than the exception.

    If you look at -- it's the same no matter what intervention you're talking about -- low carb, low fat -- anything that causes weight loss, what you see is typically -- not 100% of the time but the typical response is you'll see a certain rate of weight loss through about six months and then you start to see people regaining. By a year they've regained most of the lost weight, and if you follow them out several years, they weigh essentially the same as the group that had never even tried to lose weight at all.

    This was shown in the ten-year follow-up to the DPP study, the Diabetes Prevention Program study, which was a large, intensive study that involved weight loss. People lost like seven-and-a-half kilos, they followed them out for ten years, and after ten years the group that lost weight weighed exactly the same as the group that never even tried to lose weight.

    So there are a couple of different reasons for that. One of them is that people stop during the diet intervention very effectively over time. So --

Christopher:    Could you clarify what was the diet intervention?

Stephan:    Yeah. I don't remember all the details but it was essentially a calorie-restricted, low-fat diet. I think it may have involved shakes at some point, like meal replacement shakes. And just to add a little something to that, it was an extremely effective intervention at reducing diabetes incidence. Diabetes incidence went down by about two-thirds in the intervention group.

    It was also exercise, by the way. So exercise was part of the intervention. It was a diet and exercise-induced weight loss.

    Anyway, the point is that there are essentially two factors, I believe, in this. One is that you get reduced diet adherence over time. People are going back to their regular fattening diets, and of course, they start gaining weight again. The other thing is this opposition to weight loss that occurs via the hypothalamus leptin body weight regulatory system.

    But the interesting thing to me is if there was no regulation happening, if it was just passive weight regain, what you would expect is that the people who lost weight, once they went back to their regular diet they would start to gain weight again, but they would gain weight in parallel with the group that had never tried to lose weight. Those two lines would never meet.

    But that's not what you see. You see that the lines meet. So it's almost like the brain remembers the trajectory they were on and puts them back on that trajectory over a period of years, if that makes sense.

Christopher:    It does make sense. So the Paleo diet may be really important then because it's sustainable. I don't really speak to people that say, "Oh, I tried that Paleo thing and I hated it, and I wanted to go back." It's usually some other reason if they do stop, which is rare. It's for some other reason.

Stephan:    Well, I think that's a controversial point. I think for some people it is very sustainable, and I think the advantage of the Paleo diet is it can produce weight loss that does not require calorie counting. I'm a firm believer that calorie counting -- even though it works for some people, and I don't knock -- if someone uses it and it's effective for them, I don't knock that, but for most people, we're just not really set up to quantify our energy balance and to modify it on that basis. We've never really been creatures that consciously regulate our energy balance. It's a chore. It's hard to count calories accurately and it's just not the way that we normally interact with food.


    The way that we normally interact with food is that we eat until we're full, and then we stop eating. That's what I like about approaches like the Paleo diet is that you can do that and lose weight because the diet naturally reduces the number of calories that you eat and perhaps affects how that body weight regulatory system works, although we don't know that for a fact.

Christopher:    I wanted to talk to you about some practical examples that I've seen recently. I had a really good -- like one just the other day where someone had actually tracked -- it's not very often they get the data and this person had actually tracked some data. So they came to me and one of the main complaints was inability to lose weight, and they were already eating a Paleo-type diet -- in fact, it was a low-carb Paleo diet -- but not someone measuring ketones or anything like that.

    We did some testing on them and I think probably one of the most significant findings we found was an H. pylori infection -- which we successfully removed, we retested -- and the guy tracks his weight during these periods and there's a really steady reduction in the weight. Also, we saw a drop in his triglycerides and his fasted blood glucose went down, too. So I was wondering whether I could encourage you to speculate as whether there's any plausible mechanisms there how, maybe through inflammation, that that could be causing his weight loss.

Stephan:    So how did you eradicate the H. pylori?

Christopher:    It was a herbal program. There's something called "Mastika" that got rid of the H. pylori.

Stephan:    I don't know what that is. Is it plausible that it would have broader effects on the gut microbio -- ?

Christopher:    Yeah, I don't know. Oh, yes, certainly, yeah, but other effects I do not know.

Stephan:    Okay, all right. So essentially -- I mean, this is a bit counterintuitive, to be honest with you, because H. pylori is typically associated with a leaner body type. So there's some -- I don't know that much about this evidence but there's some evidence suggesting that the gradual eradication of H. pylori in the population at large might have actually contributed to the obesity epidemic.

    H. pylori, obviously it has some negative impacts on health or it can have negative impacts on health, but it's a stomach parasite that we've carried for hundreds of thousands of years and maybe longer than that. I think we've been carrying it since before we were even Homo sapiens. There's some speculation that maybe we have settled into this uneasy relationship with H. pylori where there's some degree of mutual benefit as well as potential risks.

    Anyway, the point I wanted to make is I don't really know what effect the eradication of H. pylori would have on body weight. It would surprise me if that were the reason for his reduction. However, depending on what effects this treatment was having on the rest of his gut flora, I mean, presumably -- the H. pylori is part of your gastrointestinal flora, right?

    So if you're taking a concoction that's having effects on your gastrointestinal flora, then it's possible that it's having broader effects on your communities in your small and large intestine. There's quite a bit of evidence in rodents that the gut flora can modify your body weight. In humans, evidence is really quite limited at this point but it's certainly plausible that it could, and I think we're going to know a lot more about it coming up pretty soon.

    Actually, there is some direct evidence. Certain types of antibiotics have been linked with weight gain in humans and we know with a high degree of certainty that they cause weight gain in a variety of different types of animals, at least low-dose antibiotics. That's why they're used in agricultural settings.


Christopher:    Right.

Stephan:    Yeah. It seems to work in humans too according to the limited evidence we have. But the other possibility, honestly, is it's one person living a human life. Human lives are complex and maybe it's just something unrelated that happened at the same time, some kind of lifestyle change or it could be any number of things. It's really difficult to isolate that one factor.

Christopher:    Yeah, that's very true, and I should have qualified it with that, that I'm not just giving this guy some Mastika gum and say, "See you later." My job is to work with him in all aspects of his life. So we're talking about his diet and rest and exercise. Stress reduction, I think, is probably really important for this particular individual. Yes, so it's very difficult to tease out the cause and effect.

Stephan:    Oh, yeah, okay. Well, if there were all these other changes occurring simultaneously, then I would be pretty skeptical about the role of H. pylori eradication specifically.

Christopher:    Okay. And then another thing I've seen some of is -- they've heard me speak on a podcast that's been like a low-carb sort of community, and they're already doing a low-carb diet but it's not really having any effect on their blood glucose or their weight anymore. What would you do if you were in that situation?

Stephan:    Well, low carb can be useful in certain applications but it's not a cure-all, and I think where people sometimes get stuck is they think that -- they get in this idea that carbs are the single source of health concerns like obesity and diabetes and whatever. They start restricting and it works a little bit, and then they keep restricting and nothing happens, and they keep restricting and restricting and it doesn't help.

    I think the reality is, as I said, it can be helpful for certain applications and certain individuals but some people don't react that well to it. Some people simply do not respond very well to carbohydrate restriction, and some of those people would be better served by actually a higher carbohydrate, lower-fat diet that's high in unrefined carbohydrate. There are studies supporting this that essentially some people experience better weight loss on low-carb diets, some people experience better weight loss on high-carb diets, and there are studies showing that low-carb diets can cause substantial improvements, at least in the short to intermediate term, in blood glucose regulation-related things like diabetes and fasting glucose and that sort of thing.

    However, there are also studies that show that very high carbohydrate, very low-fat dietary interventions can have similar effects. So it's like you have studies on both sides of the spectrum showing that people are losing weight, that people are getting off their diabetes medications, that people are having improvements in insulin sensitivity, et cetera, and I'm not talking about the wimpy low-fat diets that are usually the control diets in dietary intervention studies. I'm talking about really low-fat diets that are high in unrefined, high-fiber carbohydrate. Those types of diets actually have a fair amount of evidence behind them showing metabolic and weight improvements.

    So I would say that a lot of it comes down to individual variability. So if I were that person, I would consider trying the other end of the spectrum, gradually moving in that direction and seeing if the other end of the spectrum can offer them more help because for some people that's been shown to be true.

    So I'll just say that I receive emails all the time from people who say -- essentially, they're thanking me for broadening their thinking about macronutrients and health, because they were on a low-carbohydrate diet, it wasn't working for them, and then they tried going in the other direction, and all of a sudden things started improving. They started losing weight again, they started feeling better, et cetera. That doesn't apply to everyone but for people that it does apply to, I think it's an important realization to have and that it's not uncommon for that to occur.


Christopher:    Yeah. So I should probably qualify actually that I've had so much leverage out of going through the same process -- getting other people to go through the same process that I went through, which is to measure blood sugar and look at the number of carbohydrates that you're eating, but it would seem that doesn't work for everyone. It's useful but doesn't work for everyone. In this particular case that I was talking about, that's what the woman ended up doing and she has now lost about 20 pounds, but I don't want to speak too soon just in case we go back to that regain model that we talked about, but yeah.

    So you would say that it does --

Stephan:    What did she end up doing?

Christopher:    She was currently eating a ketogenic diet but never really got into ketosis, so she's measuring ketones and she's staying at around 0.5 mmol. Then I suggested the autoimmune Paleo protocol as a really anti-inflammatory diet, and these are all just suggestions. She looked at it and she said, "Oh, yeah, this looks good. This looks like something I could do." She was also sick of the low-carb thing, like constantly trying to adhere to the diet was difficult.

    So she tried it and she loved it. It made her feel great. She felt much better. She had some problems with swelling in her ankles that just went straight away. It seems crazy to ignore. This is someone that's waking up with her fasted blood glucose around, say, 115, 120. So it seemed like madness to reintroduce some carbohydrate but she's actually doing really well on it. So you think that's okay then to just ignore what the blood glucose meter says and to -- ?

Stephan:    Oh, so -- I mean, hasn't it gotten worse?

Christopher:    No, it hasn't. It's just the same.

Stephan:    Oh, okay. Yeah. Well, I think in that situation, essentially what I would say is that a healthy human body is capable of disposing off large carbohydrate loads in an effective and healthy manner. So when you think about somebody who has diabetes or who has pre-diabetes, they are in a state where they're not handling their glucose very well, and so there are essentially two approaches you can take. You can just reduce their dietary glucose load and that can be helpful, or you can try to fix the reason why their glucose is dysregulated in the first place.

    Ultimately, that's the approach that I think almost anyone would prefer is to really bring the body back to a healthy state where it can handle glucose once again, so I think -- and doing that doesn't necessarily relate to carbohydrate restriction. It could in some people, but it's often actually the case that very high carbohydrates, very low-fat diets are more effective at improving glucose handling and insulin sensitivity than the reverse.

    So there are essentially two approaches you can take. One is just to remove the glucose and one is to try to fix the underlying problem. I think the dietary approaches to doing that, there may be some overlap in some cases but they're not necessarily identical.

Christopher:    Okay. The other thing I was wondering about with the autoimmune protocol is it might be nothing to do with the carbohydrates or the macronutrient ratios at all and it could be something to do with food reward. So one thing about the autoimmune protocol is you remove a whole ton of things that people normally use to make food taste good, like spices, for example, so it ends up being quite a low-food-rewards diet. I'm wondering whether that might have anything to do with why people lose weight on it?

Stephan:    Yeah, absolutely. Essentially, anytime you restrict food choices, people are going to lose weight on average at least. You can look at studies that restrict carbohydrate, people lose weight; studies that restrict fat, people lose weight; studies where they put people on a vegan diet, they lose weight; studies where they put people on a Paleo diet, they lose weight -- I mean, in many cases the principles that these diets are based on are diametrically opposed to one another and would predict that the other opposed diet would cause weight gain, yet it doesn't because essentially you restrict anything and people are going to lose weight.


Christopher:    And then with the weight loss you see all sorts of other biomarkers improve and that's just a symptom of the weight loss, right?

Stephan:    Yeah, that's right. I mean, body fat mass is really, in my opinion, the number one health problem in the United States and most of the other affluent world. It contributes to virtually all of the chronic health conditions and sources of mortality that we really care about. I should qualify that not virtually all but many of them, and particularly the really top concerns like cardiovascular disease, diabetes, cancer. So yeah, it's really a central concern in my view.

Christopher:    So food rewards, how does that affect your fat mass?

Stephan:    Essentially, food reward -- I'll start off by defining it. "Food reward" is a catch-all term that people use in the scientific literature to refer to the motivating ability of food, the pleasure value of food and the learning value of food, so the ability of food to reinforce behavior. I usually use it in that narrower sense of its ability to reinforce and motivate behavior.

    So essentially, Ivan Pavlov showed that dogs learn to associate the sound of a bell with the expectation of a meal. So he would ring his bell every time he would come into their room with food, and initially, whereas the dogs would salivate at the sight of food or the smell of food, they would begin to salivate at the ringing of the bell that had been associated with the delivery of food. So essentially, what happened is those dogs' motivational centers came to learn that the bell was a predictive cue that predicted the delivery of this bolus of stuff that they liked -- calories, protein, fat and carbohydrate -- and we do the same thing.

    So essentially, our guts detect the calorie value of food and its macronutrient composition and then based on how good that food was to the digestive system and the brain based on the consequences that occur after you eat it, it sets your future level of motivation to that food. It turns out that when you eat foods that are really high in rewarding properties like very calorie-dense, high in fat, high in starch, high in sugar, high in salt, high in other rewarding things, then you will be more motivated to obtain that food in the future, and that motivational level is partially independent of how hungry you are.

    That's why people will grow a so-called "second stomach" when the dessert comes out even if they're completely full. That's the major reason why this really calorie-dense, sweet, fatty thing will cause them to continue eating even though they're full, or have a soda in the middle of the afternoon. People don't drink soda because they need the calories. They don't drink soda because they're hungry, even though that delivers a lot of calories.

    They drink it because they want the pleasure value associated with it because it's a highly rewarding beverage, and -- oh, sorry, I shouldn't have said "pleasure." They drink it because of the motivating value of that beverage because it's highly rewarding because of its properties. It's got caffeine. It's a habit-forming drug. It's got sugar. It's got calories. It's got this. It tastes good.


    I think one of the best examples of this, actually, and a way to -- because we have so many visceral and emotional attachments to food, but I think thinking about it in the drug realm helps to clarify thinking because people don't have such a visceral attachment to most drugs. So if you think about a drug like metamphetamine, basically what's going on when a person becomes addicted to metamphetamine is that meth is going into their brain and it's enhancing the release of dopamine or it's enhancing the activity of dopamine, which then reinforces all of the behaviors relating to acquiring that metamphetamine.

    So that's what the dopamine system does. It reinforces behaviors related to things that had positive outcomes for you. So when you take meth, your brain is like, "Oh, my god! This is awesome! We've got to do this again!" and so then, the next time you encounter a situation where you can get meth or you encounter a cue -- someone pulls out a bag of it, or you see your dealer, or whatever, whatever -- that triggers a level of motivation that's extreme.

    And because of the extreme dopamine release you got, that causes a level of motivation for meth-acquiring-related behaviors that exceeds the level of motivation for everything else in your life. So those behaviors take priority over things like personal hygiene, health, personal relationships, jobs, food, water, all the things that would normally be high priority. Meth is number one. Those behaviors are the priority.

    So essentially, addictive drugs like meth hijack the normal, natural reinforcement process that allows our brains to learn how to execute behaviors that make good things happen for us. When we eat food, your gut and your brain detect how "good" that food was based on its properties and reinforce your motivation to obtain that food in the future accordingly. So it's the exact same system except it's getting activated to a more natural degree rather than an extreme degree like it would during drug ingestion. You're not going to probably break into someone's house and steal a TV to buy a slice of chocolate cake, but it's a similar process that's just occurring to a more modest and a more natural degree, and it can still --

    When you have foods that are extremely rewarding -- and I would say that a lot of our foods today are unnaturally rewarding by evolutionary standards. Hunter-gatherers didn't have chocolate cake. They didn't have potato chips, et cetera, et cetera. They didn't have pizza. When you have these foods that are unnaturally rewarding, they can create, they can cultivate motivational states that cause us to prioritize food-seeking and consumption behaviors that are counterproductive for our health and well-being, because we're motivated enough, not necessarily addicted, but we're motivated enough that we will seek and eat those foods even in the absence of hunger and in the absence of an energy need.

    So essentially, I would say that food reward, it causes us to learn and to be motivated to consume food to excess, and it causes us over time to develop deeply ingrained unhealthy eating patterns that are based around these highly rewarding foods. It is possible to break out of those but it requires effort and willpower. It requires essentially that you swim upstream against a lifetime of accumulated behaviors and habits. So I would say that the rewarding value of food is acting via its ability to increase calorie intake.

Christopher:    Okay. So there's obviously a million shades of gray here in terms of the individual and what foods they're finding so rewarding.


Stephan:    Mm-hmm, absolutely.

Christopher:    And then do you think there's any place -- I've asked a couple of people the same question now -- so do you think there's any place then for Paleo equivalence of the old crap that people were eating before they started this diet and lifestyle? Almond flour, dates, honey?

Stephan:    Well, I mean, to me that's not Paleo.

Christopher:    Okay.

Stephan:    Well, honey is Paleo.

Christopher:    Yeah, but using it as an ingredient to make highly palatable treats.

Stephan:    Yeah, yeah. That's not Paleo. I mean -- that's just not Paleo. I would say that different people define "Paleo" differently, but to me that's clearly not Paleo. To Loren Cordain that's not Paleo. It really depends on how you define it.

    So if you define Paleo as a food that is made using ingredients that might have been similar to those accessible to our ancestors, then yeah, sure, you can make muffins out of almond flour and whatever, chocolate chips in it and drizzle honey on it. But I think, from my perspective, it's much more useful and much more informative to take a broader perspective of what Paleo is. Paleo is not just about the ingredients, it's about how the food is presented, because that has a massive impact on how much of the food we're going to eat.

    So if I were to give you, for example, a deconstructed pizza, like plain dough next to some plain salami next to a block of plain cheese, and a few basil leaves or anchovies or something, you would eat a lot less of it. And I'm saying "you" in a broad sense. I don't know whether you in particular would eat any of that at all, but the hypothetical person would eat a lot less of that than they would eat of an actual pizza. I'm not saying that either scenario would be a healthy scenario, but certainly it would be healthier to eat less of it.

    So I think it's very critical to consider the context in which we're eating the foods and the forms in which we're eating the foods because that is a very important part of how are ancestors interacted with food and how are ancestors remained lean.

    If you look at -- I mean, even a simple Paleo diet, a relatively simple one like what Loren Cordain would recommend is far more palatable than what actual hunter-gatherers would eat. If you look at a real hunter-gatherer diet, they're just taking chunks of wild game and throwing it in the fire, and they're collecting wild fruit.

    That's probably one of the more palatable things that they're eating, but they're not making cobbler out of it. They're not even cooking it. In most cases, they're eating fresh fruit right away. They're not sautéing onions, they're not baking things, they just don't have the technology to do all those things, and a lot of the things that they eat are not particularly palatable even to them. I mean, some of them are.

    If you look at the !Kung San foragers of the Kalahari Desert, some of the things they eat are tasty. They eat mongongo fruit and mongongo nuts. Mongongo fruit is described as tasting like a date, and the nut is like a hazelnut. But a lot of the other things that they get to make up their calorie intake, like certain other tubers, are bitter or really fibrous, and the reality is they eat what they can get.

    Some of what they can get is pretty good stuff, some of what they can get is not that good stuff, but all of it requires effort. So not only is it varying in how tasty it is but if you have to walk three miles to get your meal, you're going to require a higher level of motivation or a higher level of hunger before you execute that behavior and ingest those calories.

    So I think there's a prominent role for the food environment and also for the presentation of food, and that's --

Christopher:    Okay. So that's kind of interesting. I've not -- sorry.

Stephan:    That's okay. I'm done.

Christopher:    Okay. Yeah, I was just going to say that's interesting. I've not really thought about that before. My wife is a food scientist and an excellent cook and she does a really good job of presenting food in a way that I never could. It looks fantastic and she takes photos and all the rest of that good stuff. So that might actually then be a mistake in terms of getting people to eat the right amount of food.


Stephan:    Well, my perspective is it's all about your goals. Food reward and food palatability is not inherently harmful. At least in my opinion, it's not this bad thing that we need to minimize. It just depends on your goals. If you're someone who's trying to gain weight, then that could be a valuable factor in your diet to increase the reward value and the calorie density, surround yourself with more palatable foods. That could be what you want to do. If you're trying to lose weight then it is going to be counterproductive.

    If you don't care about your weight then it might not matter so much for you, or if you find that -- different people vary in how they respond to different factors, so some people -- and this has actually been studied -- some people, palatability of the food has a very large impact on how much they'll eat and when they decide to stop eating. Other people it has less of an impact, and that relates at least in part to genetic factors.

    So it depends on you and it depends on what your goals are. Again, I like to try to not portray food reward as a negative thing. What it is is a tool that can help you achieve your goals.

Christopher:    Yeah. So if the goal then was to try and get more people interested in cooking and eating a Paleo type of diet, then it might still be beneficial. Sometimes it's easy to forget that only a teeny, tiny fraction of the people certainly in the U.S. are eating this way. So maybe it's then a good thing.

Stephan:    Well, yeah, and I think it could be viewed that way. If you look at any kind of diet, almost any kind of diet that's popular, almost all of them try to maximize the palatability of the food by adding spices and whatever because they're trying as hard as they can to get people to stick with it. That's the problem is that while limiting food reward and palatability can benefit weight loss and can help you gain control over your eating behavior, since the reward value and the pleasure value are part of the enjoyment of food, it can make it more difficult to stick with it. I mean, most people would completely fail if they try to eat a real hunter-gatherer diet. A real hunter-gatherer diet would be completely unpalatable to most Westerners, or at least largely unpalatable and extremely bland.

    So I think you run into this issue of effectiveness versus adherence, and for a diet to become popular, you have to really portray it in this positive light where it's like, "Oh, man, you're going to love this diet. It tastes so good. You're going to be able to eat this and that," and try to portray it as positive instead of focusing on what the diet really is, which is a restriction, because every diet is restrictive in some way. But that's not the a way to sell a diet or -- I'm using "sell" in a broader term of like promote a diet or to get people excited about a diet. So there's this conflict there, I would say.

Christopher:    And then finally, I wanted to ask you, are there any general rules or guidelines that I should be adhering to if someone comes to me asking -- and their goal is to lose weight and they're already on a Paleo-type diet?

Stephan:    Yeah, sure. Yes, absolutely. I think one of the most important and overlooked -- well, let me take a step back here. I'll start with just discussing the Paleo diet a little bit.


    I think one of the reasons why the Paleo diet is effective for weight loss in many people is that it already incorporates many of the factors that have been shown to promote reduced calorie intake and weight loss in humans, and so at least -- different people have different definitions of the Paleo diet but according to Loren Cordain's version, if you look at it, it's high in protein, it's low in calorie density, it's high in fiber, it is restricted, it reduced reward and all of those things, and it eliminates the most common, highly palatable, calorie-dense foods that provoke overeating in people, those things that are really unnaturally palatable and rewarding. All of those things contribute to eating less and losing weight naturally without feeling like you're depriving yourself. So it's maybe by happenstance or maybe not, it's a confluence of factors that benefit weight loss.

    But that's not the end of the story because the diet composition is only one factor that influences body weight, and I think another important factor, another very important factor is what your food environment is. Is there food lying around your house? What kind of food is it? Is it tempting? Is it something where you'll find yourself sticking your hand into a bag of potato chips when you're not hungry in the middle of the day because it's on the counter? Or maybe you weren't hungry until you saw the bag of potato chips, and then all of a sudden you're hungry.

    Are there doughnuts in your break room at work? Is there Hershey Kisses on your secretary's desk? All of those things like that. What restaurants are there on your walk or your drive home from work? How many food advertisements are you seeing per day?

    The average U.S. adult used -- something like -- I can't remember exactly how many -- I think it's 16 food advertisements per day on television. So that's an onslaught of food cues that you're getting at all times that are reminding you of the possibility of eating a hamburger or a piece of pizza or drinking a soda or whatever. Those are cues that trigger your reward system to generate the motivation to obtain those foods. Those advertisements work. That's why those companies pay billions of dollars a year to put them on TV. They're highly effective at stimulating our motivation to obtain those specific foods.

    So I would say that controlling your personal food environment, controlling your exposure to cues, and the availability of food is really key. If you walk around my kitchen and you want to just grab something to eat, the only thing you're going to find are unsalted nuts and fresh fruit. There's nothing else in my kitchen that you can just grab and eat without putting some amount of preparation work into, and I think that's really important.

    You can have healthy foods around your kitchen, but if they're under your nose all the time and you're looking at them all day and they're tempting, you're probably going to end up eating more than if there was nothing particularly tempting there. Unsalted nuts to me, I know for myself personally that I will only eat them if I'm genuinely hungry. They taste fine, they taste good, but it's not like a bowl of potato chips where I could just sit there and destroy it regardless of whether I'm hungry or not, and if --

Christopher:    Since they're roasting in the salt that adds the palatability, that means you can overeat them?

Stephan:    Yeah, yeah, for me, and salt is a palatability and reward factor for everyone or almost everyone. But not everyone is going to necessarily have the same threshold that makes them want to eat something when they're not hungry. Maybe some people, just having nuts around is too much, or maybe some people having salted roasted nuts is fine. So it's not necessarily going to be the same for everyone but that's the balance that I find for myself, and the principle is you don't have things in your food environment that you are going to be tempted to eat if you're not hungry, so only things that are not attractive enough that you will eat them if you're not hungry.


    So at home, you get rid of calorie-dense snack foods that are on your counter. You don't give yourself visual cues for food. You get rid of the ice cream in your freezer. At work, you get rid of foods lying around. You talk to your co-workers about, "Let's not have these doughnuts in the break room anymore," et cetera, et cetera. I think those things are very, very, very important because even if the foods that you are surrounded with are healthy, you can still overeat them if you create a situation for yourself that favors overconsumption.

Christopher:    All right. That makes a lot of sense, yeah, and I had not really thought about it as carefully as I should have done. Our environment is exactly the same. On the very rare occasion that I do go looking for food and it's not expected -- so that kind of snacking behavior, it's exactly the same -- I open our fridge door and there's usually like Swiss chard and some defrosted lamb shanks and really absolutely nothing. But possibly some U.S. Wellness Meats is about the only thing you can just take out of our fridge and eat, and I had not really thought about the importance of that and I had not really been talking to anyone else about that either. So that's a really good piece of advice.

Stephan:    Yeah, it's critical, and that's exactly it. Same thing here. You open my fridge, there's plenty of food for dinner if you're willing to cook it, but when you create an effort barrier for eating those foods, you're not going to go passively eat them.

    So one of the main determinants of food intake in humans and all animals is how much effort you require to eat it. If you took the person who eats fast food every day by driving through the drive-thru and you created a situation where they had to walk three miles and climb a tree to get their meal, they are going to end up eating less than they would if they were just driving through and getting that food. So creating an effort barrier even if it's a small one, even just putting things on the top shelf of your pantry where you have to get on your tiptoes, just little things like that can have a substantial impact on your likelihood of consuming the food.

Christopher:    That's another really interesting idea. Well, Stephan, thank you so much for giving me your time today. I'm really, really grateful. This has been a very interesting conversation.

Stephan:    Okay. My pleasure, Christopher.

Christopher:    Cheers then. Thanks.

Stephan:    Okay, bye.

[1:07:33]    End of Audio

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