Welcome back to the Healing Pain Podcast with Dr. Stephan Guyenet
Are you finding it hard to resist sinking your teeth into that third donut? Do you find that your pants are getting a little bit more snug than it was just a couple of weeks ago? You are not alone. The struggle with weight loss has increased over the years with the onslaught of food choices in great portions. Shifting your focus from your gut to your brain may be the answer. Dr. Stephan Guyenet takes us into the inner circuits of the brain and delivers profound insights on how weight loss begins with the brain and why we overeat. These insights provide understanding on what to eat and help develop practical guidelines for eating well and staying slim.
On this episode, we are talking about the real science behind why we put on extra weight and the simple strategies you can begin to implement into your life that can take the weight off or better yet prevent you from gaining weight in the first place. This is important because if you’ve been studying my work for a long time now, you know that those who are overweight, obese, or carrying extra weight tend to have significantly higher levels of pain as well as other chronic pain syndromes. The best way to achieve weight loss is a combination of healthy nutrition changes combined with exercise. There’s a lot of other variables that affect body weight such as your stress level, appetite, sleep, and even your brain’s reward system.
Ancient brain circuits that are no longer needed in our modern life can lead your appetite and food choices astray. These circuits don’t care how you look in a pair of skinny jeans or if spring or summer is on the way and you’re going to be putting a tank top on. My guest is Dr.Stephan Guyenet who earned a PhD in neuroscience and spent over twelve years studying the brain science of obesity and eating behavior. If you’re looking for an expert with a no-nonsense, 100% scientific and evidence-based solution as to why we put on extra weight, Stephan is the one you should be following.
Hunger, The Brain And Why We Overeat with Dr. Stephan Guyenet
Stephan, thanks for joining the Healing Pain Podcast. I’m excited to talk to you about some of your research and some of the tips and strategies we can share with people.
Good to be here.
People are used to hearing information and they love learning about the brain and how the brain influences everything that’s going on in our life. We know the brain has a lot to do with chronic pain, but specifically, we know that weight loss can help people with chronic pain, help alleviate their pain, help alleviate inflammation. Why should a conversation about food and weight loss begin with the brain?
The fundamental insight that I had, that I know I was not the first person to have but that a lot of people haven’t considered is that the brain generates all behaviors. It generates all feelings, it generates all impulses. Anytime that you decide to eat something or decide to eat one thing over another or decide to use a certain amount of something, that behavior is generated by the brain. When you decide to engage in physical activity or not engage in physical activity, that’s generated by the brain. When you feel a craving, when you feel hunger, when you feel full, all of those things are generated by specific brain circuits. The brain is a frame for viewing, eating behavior, and body fatness through because that’s the thing that generates so many things that are relevant to it. I talked about behavior, but the brain also actively regulates body fatness through a feedback loop.
Like chronic pain, there are circuits in the brain that are being fused together. When we talk about chronic pain, we look at three areas. We look at the prefrontal cortex, we look at the somatosensory cortex, and we look at the limbic system. Even with chronic pain, there’s no one area that’s involved. When we start to talk about weight and fatness, what areas are we starting to key in on?
There are a number of parts of the brain that are involved in some way or another. Depending on how directly or indirectly you want to talk about how closely they’re involved, then you could talk about nearly the entire brain. The one that is most intimately involved in food related decisions is the hypothalamus. That’s the one that has probably been studied for the longest time. The first research into its role in body fatness goes back to the late 1800s. That is the part of the brain that regulates your long-term energy status of your body, particularly your body fatness. It measures how much body fat you have using the hormone leptin, and some other signals as well, and integrates that into a signal that controls a lot of outputs related to your long-term energy status, like your appetite and your metabolic rate. Then there’s your brainstem, specifically apart that includes your nucleus tractus solitarius and your area postrema that regulates your meal-to-meal satiety or fullness that’s receiving signals from your gastrointestinal tract that is essentially a signal of your short-term energy status.
What it is that you just ate? It collects a ton of information, integrates that altogether into a signal that tells you when to stop putting the fork to your mouth. There’s the ventral striatum or nucleus accumbens and many associated brain regions such as the ventral tegmental area, which produces dopamine and much of the frontal cortex that receives signals related to that, but particularly the orbital frontal cortex which is related to decision making. Those structures are intimately involved in your basic motivational drives. Are you feeling hungry? Are you feeling sexy? Are you feeling cold? Are you feeling hot? Those are the circuits that will select your motivational drives based on your body’s internal state and what’s going on outside your body that you are perceiving through your sense organs and generate these motivational drives, like cravings, that can push us to eat. Those systems are all engaged to various degrees at all times and depending on what’s going on inside your body and what’s going on outside of your body, different systems can be dominant in different situations.
As you were talking, the first thing that comes to my mind is, “How much of this is learned by early experiences in our environment?” It always goes back to that nature or nurture conversation. Many people realize that their challenges and struggle with food may have started in childhood or when they were younger or with their family values.
Learning plays a huge role. The ventral striatum or nucleus accumbens, the ventral tegmental area, the orbital frontal cortex, the way that those respond to food cues is very much learned. When I say learning, people often think of sitting down and you’re looking through a textbook and you’re absorbing information, but that’s not what I’m talking about. I’m talking about a form of non-conscious implicit learning that sets our basic motivational drives. What happens is your brain is set up to seek certain things from food. The brain, over the course of millions of millions of years of natural selection, was selected to try to favor foods that are higher in certain substances that would have supported the survival and reproduction of our ancestors. Things like carbohydrate, starch and sugar, fat, protein, the specific amino acid glutamate, which is that meaty umami flavor that’s in monosodium glutamate and bone broth and meat.
Salt is the only one that doesn’t supply calories. The brain is very much attuned. It’s hardwired to seek food properties that deliver calories to the body, presumably because that was so important for the survival of our ancestors. You go to any culture, you’re going to find people who like glutamate. You’re going to find people who like fat. You’re going to find people who like sugar. Everybody likes that. That’s hardwired into human nature. What you’ll find that differs is the different aromas and appearances and textures of different food. Even though everybody likes fat, maybe a person from China wouldn’t appreciate the smell of stinky French cheese, or maybe a person from France wouldn’t appreciate the smell of authentic Sichuan cooking. The reason is that we’re not hardwired with all the flavor and texture preferences. All those sensory cues, those are things that we learn by virtue of their repeated association with the fat, the sugar, the starch, the protein, and the salt.
When you eat a food that contains a lot of those things, like a slice of pizza, you get dopamine released in your brain. At once, you get a signal coming up from your digestive tract that’s telling your brain that there’s lots of starch, lots of fat, some protein in this food, concentrated. You’re getting a strong signal that spikes dopamine in your brain. That’s a hardwired response. You get spiking dopamine in your ventral striatum, nucleus accumbens, and that tells your brain to stamp in and remember all the sensory cues that you experienced. The smell of the pizza, the appearance, the texture, what the box looked like, the shape of the slices, where you were at the time, who you were with, what the situation was. All those things are stamped into the brain and they become motivational triggers. The next time you see them, your brain remembers what they were associated with. This is called Pavlovian conditioning, a very simple psychological concept. It remembers all those cues and those trigger, that motivational response because your brain knows that those are signals that it can get this excellent thing.
It signals the availability of this excellent thing. It kicks in these basic non-conscious motivational circuits. Your conscious perception of that is the feeling of a craving, of wanting to eat the pizza or wanting to eat the ice cream. That is a learned response. Your early life experiences are particularly malleable in many ways, including informing your food preferences. The foods that you eat early in your life are going to be disproportionately important in setting up which of those sensory cues, what food is it that you’re going to crave when you smell it, or when you see it, or when you taste a little bit of it. Are you going to like soda as an adult? Are you going to like Twinkies as an adult, etc? That’s determined to a large extent by your early life experiences.
My heritage is Italian and in the Italian culture, especially with a nice meal, they like to serve a little bit of bitters and it’s not a lot. It is an alcoholic drink, but it’s only very little bit. I’ve always asked my relatives, “Why do you serve bitters before a meal?” The answers were always twofold. One is it helps prepare your palate for a meal. Two is it improves digestion. I often wonder if the behavioral habit that they’ve created is priming my brain and potentially releasing digestive enzymes maybe a little bit ahead of time to help my body prepare and digest the food that’s about to come into it. Is that another real life example of what you mentioned?
That could well be. Another thing is that many of these bitter substances, they stimulate receptors in the gastrointestinal tract and they do increase the secretion of digestive enzymes and gastric motility. They do seem to enhance digestive function. The reason is simply that a lot of bitter compounds in nature impair the digestive process and so your gut is like, “We got to ramp it up to make up for this difficult situation we’re in.”If you choose the right bitter compounds, you’re stimulating digestion without impairing your digestive process.
It’s also interesting because the Italians like bitter flavor where most Americans try to avoid it and very deterred by a bitter flavor in their diet.
It depends on the context. You’re right in many ways, but Americans like beer. One of the key ingredients in beer is hops, which is quite bitter. Bitter flavors are inherently aversive to humans and to many animals. Bitter flavors signal potentially toxic properties of the food. You can learn to like bitter things if they’re repeatedly associated with those properties. I was talking about. This is the Pavlovian learning. If you consistently have the bitter flavor of hops, but you’re also getting this dopamine-stimulating alcohol every time you eat it, every time you encounter it then your brain is going to learn, “We didn’t like the bitter stuff at first, but now we see that it’s good.”
If you remember the first time you tasted beer, most people will remember it being truly awful, same for coffee. Coffee and beer both have habit forming drugs in them. They both have reinforcing drugs that stimulate the dopamine system. Even though they taste bad at first, you have them a few times and then they start to taste good. That’s how that system works. It works the same way with many other foods. It doesn’t have to be a drug, it can be a food. Overtime, we learn to enjoy the bitter flavors of like kale or brussels sprouts or other vegetables. Even though as kids, we probably didn’t like them, but you have them with fat and salt enough times and your brain says, “It tastes better, but it brings me the fat and salt, so I’m okay with it.”
You mentioned food cues before and I want to give people some examples of what maybe beneficial food cues that support healthy eating and those that might lead them down to weight gain or something that’s not so healthy.
I think the concept is very simple. You provide food cues for things you want to eat and you minimize food cues for things you don’t want to eat or things that aren’t consistent with your long-term goals. You have competing goals systems in the brain. You have the short-term instinctive that wants to eat the brownie and then you have the long-term that wants the leanness and health. If you set up the situations in advance, you can essentially undercut the short-term system or not drive it to begin with by providing the right cues. To make that a little more concrete, if you have an open bag of chips in your kitchen, you’re going to have to use willpower to fight yourself not to stick your hand in there and grab a handful. If you don’t have any chips in your house at all, you have to be motivated to go to the store and buy chips to eat them, so you’ll probably not going to do it. Even if they’re just a closed bag in your cupboard, out of sight on the top shelf, you’re going to be less likely than if it’s open on the counter. For most people, the concern is wanting to avoid weight gain. If that’s the situation, I would say minimize food cues in general, in your personal surroundings.
If you walk into my kitchen, there are very little food that you can grab and eat. The stuff that’s there is there to grab and eat, there are little effort barriers to eating it. I would have to unscrew a lid of a jar to get raw almonds and there are no roasted salted almonds because those are too tempting. I’ll eat too many of those. You reduce the value of the goal and you create little effort barriers. There are oranges that if I’m hungry, I’ll eat an orange, but I have to be hungry to want to peel it and eat it. If I’m not hungry, I’m not going to idly eat it. You want your home and your work environment to be like that. You don’t want to have tempting food cues hanging around and you want the foods that are around to be foods that are not that tempting and require a little bit of effort to begin to eat. If you do it like that, you’re giving yourself the opportunity to eat. If you’re really hungry, if you really need it, you’re not creating a situation where you’re going to have to battle yourself to avoid undermining your own long-term goals for eating behavior and health and weight.
Set up the kitchen correctly. The kitchen is where we go for food and the kitchen is where many of us spend a lot of our time, as well as time where we enjoy activities with people. Nutrition science, food, all of it can be confusing. There’s a lot of information out there. I want to talk a little bit about macronutrients as it relates to disease and as it relates to body fatness. When we say macro nutrients, we’re talking about protein, carbohydrates, and fats. There’s a lot of controversy around what the right ratio is and if one ratio is too high. Does it lead to things like diabetes or obesity? What has your research unveiled on that topic?
I’ll start with obesity. There’s been many studies done on the effects of macronutrients and the effects of calories on body fatness. What you see if you look at the most tightly controlled studies, the best evidence available, you see quite consistently that the calorie content of the diet, and not macronutrients, is what determines body fatness. When I say that it can have some misleading implications, I want to make sure that I explained myself fully. What I mean is that macronutrients don’t matter to body fatness, independently of calorie intake. If you fix calorie intake at a certain level, you can vary the proportion of carbs and fat to extreme degrees and it makes no difference. You can even vary protein and it makes little to no difference. Calories are the factor that matters. The macronutrient composition of your diet can affect how many calories you eat. It can have an effect via calories. People who go on very low-fat diets tend to eat fewer calories and they tend to lose fat. People who go on very low carbohydrate diets tend to eat fewer calories and they lose fat.
Macronutrients can impact how many calories you eat. If we’re talking about carbohydrate and fat, the further you go to either extreme, the fewer calories you’re going to eat and the more weight you’re going to lose. It’s always funny to me to see like you have proponents of the really low-fat diets and you have proponents of the really low-carb diets and they’re both saying very similar things. They’re like, “This one macronutrient is bad, and it will make you fat. The other one is good and will make you slim.”They’re saying the exact opposite thing and they both have data to support both of their positions. The problem is that they don’t acknowledge the data from the other camp. The only way to resolve that problem is to say, “It depends on the context and either one can be fattening depending on the context.”
What it comes down to is the idea of restriction. If you’re eating as much as you want of everything, you’re going to tend to eat a lot of calories. If you restrict a major part of your diet, you’re going to eat fewer calories, especially if you restrict it to a great degree like you would see in a very low fat or very low carbohydrate diet. Protein tends to suppress calorie intake and body fatness and tends to support lean mass during fat loss. Protein is particularly important. If you eat a higher proportion of protein in your diet, your overall calorie intake will be lower and it will tend to attenuate some of the starvation responses that your body will kick in as you start to lose weight. It will mitigate those things to a degree if you’re eating higher protein and make it easier to lose and maintain that loss.
How would you define higher protein? What percent would you say it is defined as?
There are different ways to define it, but if we’re talking percent, I would say something like 30%.
When we talk about macronutrients, there’s two, carbohydrates and fat. This seems to be the year of fat with the ketogenic diet. When we think about carbohydrates, are you saying there’s not a difference between, let’s say a whole grain versus a processed grain, like a cracker as far as the influence of body fatness on someone?
There may be a very small difference and the reason is that you absorb less of the calories from whole grain food. Your digestion is a little bit less efficient. Since you’re absorbing less of the calories, it’s probably less fattening, but small difference. If you’re not keeping calories controlled in a laboratory setting, you’ll find that you probably eat fewer calories of the whole grain food because it’s more filling per calorie.
How would what we’re talking about frame, let’s say the US Dietary Guidelines, and the controversy around the guidelines and its influence on the obesity epidemic because they definitely have changed the guidelines over the decades?
They have changed the guidelines. Our understanding has evolved, and the recommendations have evolved. There are different perspectives on this, but it’s hard to argue that the dietary guidelines contributed to the obesity epidemic. If you go back and read what the guidelines were, the US Government has been giving dietary guidelines for over a hundred years but the ones in 1980, they marked a more substantial shift in the types of advice that was given. If you look at them and you read them, there’s not a whole lot to argue with. Some people will argue that they made us eat more sugar or more refined carbohydrate. If you read the recommendations, one of the key points they make is to eat less sugar. That’s one of the things that’s emphasized more than anything else in that document. They specifically say, “Talk about if you want to lose weight, you should eat both less fatty foods and less sugary foods.”They emphasized eating unrefined foods. It’s not like, “Go out and eat a bunch of Wonder Bread.”It’s emphasizing whole grain foods or whole foods in general. I will say that it does have low-fat.
The original guidelines had a lower-fat slant, but they weren’t militant about it. They recommend nuts. You can eat eggs. It says you can eat meats. It’s not like a low-fat vegetarian type of advice. It’s somewhat lower fat. You have to take what they were recommending in the dietary guidelines and you have to compare that to what Americans eat. The average American eats a horrible diet. In 2007, the CDC and some of their surveys collected data on where the majority of calories coming from in the American diet. They published this in the 2010 Dietary Guidelines Report. The number one source of calories in US diet at the time was grain-based desserts. I’m talking about cake and cookies and pastries. That’s the number one source of calories. People were not following the dietary guidelines. That’s my point. Also, in the top ten were pizza and soda, sports drinks, fried chicken, ice cream.
The American diet is not a diet that anyone would think would be slimming by any stretch of the imagination. It’s an extremely fattening diet that the average person eats in this country. To say that the guidelines caused that when the diet that we eat doesn’t resemble the guidelines in any form, that’s disingenuous. If we had followed the guidelines in letter as well as in spirit, we would be a lot leaner and healthier than we are. People have made arguments that the guidelines were permissive of the food industry, creating low-fat junk foods that technically qualify for the guidelines but aren’t really good for you. It’s possible that it contributed to the fattening consumer landscape that we have.
I can’t see the guidelines changing that much going forward. It’ll be interesting to see how it starts to pan out. Your book is called Hungry Brain. You have a PhD, so you’ve spent a lot of time in the research and looking at the data. After writing the book, was there something you looked back on and say, “I haven’t come to the conclusion about whether it’s fat or carbohydrates or calories.” What is the question that’s still in your mind after reading all the research?
There’s a part of the brain called the hypothalamus that regulates your body fatness. It does so by detecting circulating hormone leptin that’s produced by fat tissues. It regulates your body fatness, like your home thermostat regulates your house temperature, by something called the negative feedback loop. It has a set point, like your home thermostat has the temperature set point. Your hypothalamus has a body fat set point and that’s the thing that it defends against changes. If you start gaining weight, it’ll cut your appetite and push you back down. If you start losing weight, it will ramp up your appetite among other things to try to bring you back up. People with obesity have a higher set point. People with obesity, their brains are actively defending that higher level of body fatness. That’s why it’s so hard for them to lose weight.
A person who’s been lean for his or her entire life doesn’t have to work that hard to stay lean. A person who is obese, who has obesity, and then becomes lean through weight loss has to work really hard to maintain that. If you look at people who went through the Biggest Loser show, most of them have regained most of that weight over time. Those are people who are highly motivated to lose weight and keep it off and most of them were unable to do it because it’s extremely difficult. You’re fighting your own brain. The question is people gain weight over the course of their lives. How does the set point increase? How does a hypothalamus that’s defending a lean body state become a hypothalamus that’s defending an obese body state? We don’t know exactly how that happens. That’s one of the biggest questions that’s hanging over the obesity field that most people aren’t even aware of. It’s quite a critical question for understanding how obesity occurs and how we might be able to prevent or even reverse it.
There are pharmaceutical companies that look at, “Can we leverage this? Can we maybe look at targeting that part of the brain?” Why has that not happened?
It has happened. There was a $12 million payment given to the university that discovered leptin by Amgen for the rights to develop it as a weight loss drug. This was back in the mid ‘90s and it turns out the problem is that leptin doesn’t quite work the way people thought it did at the time. Leptin is more about preventing weight loss than it is about preventing weight gain. If you give someone leptin, they will lose weight, but it doesn’t make them go from obese state to lean state. It’s not about defending the upper end of the weight spectrum. It’s about defending the lower end and making sure you don’t starve. It’s a barrier to weight loss but not a barrier to weight gain. That makes it a drug that’s not very effective. It is approved for use in lipid dystrophy, which is a problem of fat storage that is rare and not so good for you. It helps improve insulin sensitivity in that setting.
One thing that the research is showing is that even though leptin will not cause a person with obesity to lose large amounts of weight, it does seem to help people maintain the weight loss. Normally, what happens is you lose weight, your body fat level drops, your leptin level drops, your brain hears it, and that’s what causes it to kick in that starvation response that makes you hungry that makes it hard to maintain weight loss. If you maintain the leptin level at your pre-weight loss level by injections, you’re preventing the level of leptin from dropping as you lose weight. That turns off all of these responses that the brain kicks in normally that makes you regain weight. You don’t see a decrease in your metabolic rate, you don’t see an increase in responsiveness to food cues, you don’t see an increase in hunger. It may be that it could be useful at preventing weight regain following weight loss. The pharmaceutical company has got burned so bad in the ‘90s by leptin that they might not be coming back into that sphere yet. Other thing is that it requires an injection. It’s a pain as far as drugs go.
We’ve talked a lot about food. We should at least talk regarding activity and exercise and how that’s important and what effect it has on the brain with regards to weight loss and body fat.
A lot of people are hearing that exercise is ineffective for weight loss. There is some evidence suggesting that it’s not very effective, but it’s been somewhat exaggerated. The problem is that when you do a study where you ask people to exercise, a lot of times, they don’t do it. If you don’t see that the exercise causes weight loss, if they didn’t do the exercise, it’s not very informative. What I did is I looked at studies where they monitor people and people had to come into a facility and do the exercise so it’s enforced, it’s observed. When people have a regular exercise routine that’s burning substantial numbers of calories, they do lose weight and they lose a fair amount of weight. Furthermore, people tend to feel better. You feel better when you’re more fit, when you have a lower level of body fatness, when you have more muscle. It can be helpful for a weight loss, but it has an important role in preventing weight gain to begin with.
Most of the evidence comes from animal studies because it’s hard to do these studies in humans. If you put an animal in a fattening environment, if you give it free access to lots of human junk food, which is fattening in every species, if you give them access to exercise, that will partially prevent the weight gain that they experienced. It doesn’t completely prevent it, but it partially prevents that weight gain. It’s a protective factor that can make people more resistant to the fattening effects of the environment that we live in. Beyond the body fatness issue, if you want to perform well in life and feel good in life to perform at your highest level of physically and cognitively and age well, I don’t think you can ignore physical activity. It’s absolutely required for maximum performance and well-being and healthy aging.
Being a nutritionist, I love nutrition. It’s great that we have taken to the internet to educate people, but there’s definitely a subset that talk about nutrition only and don’t look at other aspects of our environment. Exercise is a big factor in that. The things you mentioned regarding mood and cognition and aging, the research around that is undeniable as far as how important that is in someone’s life. Can you tell us how people can learn more information about you and some of the great things you have?
The best place to go if you want to learn more is my book. It’s the most comprehensive and most well-written thing that I’ve ever produced. I would recommend the book above anything else. I also have a website and that’s StephanGuyenet.com. You can also do WholeHealthSource.org. I’m pretty active on Twitter @WHSource. The stuff I tweet is fairly technical. It’s a lot of scientific articles. Sometimes, I’ll a do a little bit less technical commentary. If you’re interested in obesity science and eating behavior and how it all connects with health and smattering of neuroscience, you might be interested in that.
I want to thank you for being on the podcast.
About Dr. Stephan Guyenet
Stephan J. Guyenet is a researcher, science communicator, and science consultant. After earning a BS in biochemistry at the University of Virginia, he completed a PhD in neuroscience at the University of Washington, then went on to study the neuroscience of obesity and eating behavior as a postdoctoral fellow. He spent a total of 12 years in the neuroscience research world, resulting in publications in scientific journals have been cited over 1,800 times by his peers. His general-audience book The Hungry Brain was named one of the best books of 2017 by Publishers Weekly.
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