#636： Why You Overeat and What to Do About It
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Summary
We all know the basics: don t consume more calories than your body needs, and yet many of us still overeat, sometimes continually, sometimes to the point where it leads to obesity, diabetes, and a significantly lower quality of life. Why does our behavior betray our intentions to be lean and healthy? My guest argues that the answer lies in the ancient instincts of our brains that no longer fit the environment of the modern world.
Transcript
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Brett McKay here and welcome to another edition of the Art of Manliness podcast.
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We all know the basics of losing weight, don't consume more calories than your body needs.
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And yet many of us still overeat anyway, sometimes continually, sometimes to the point where
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it leads to obesity, diabetes, and a significantly lower quality of life.
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Why does our behavior betray our intentions to be lean and healthy?
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My guest today argues that the answer lies in the ancient instincts of our brains that
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no longer fit the environment of the modern world.
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He's a neuroscientist, obesity researcher, and the author of The Hungry Brain, Outsmarting
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We begin our conversation with what's changed in our country to turn obesity in an epidemic
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and why Americans started to gain more weight in the 1970s.
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We then dive into exactly how the reward system in our brain leads us to eat more than what
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we need to, how modern manufactured foods like Doritos, one of my favorites, hijack
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this reward system, and the factors that ramp up our cravings, including the buffet effect.
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Stephan then explains how to push back on this desire to overeat, including reevaluating the
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assumption that all your food you consume has to be tasty and delicious.
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From there, we turn in the role that the hormone leptin plays in appetite regulation, how it can
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make it hard to keep the weight you lose from coming back, and the best techniques to manage
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We end our conversation with the role stress and sleep play and weight gain.
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After the show's over, check out our show notes at awim.is slash hungrybrain.
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All right, Stephan Guillenet, welcome to the show.
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All right, so you are a neuroscientist who studies the central role the brain plays in regulating
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hunger and how appetite leads to overeating and weight gain.
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But before we get to those specific dynamics, let's take a big picture view of what's called
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I think in the book, you said that we're at something like 30 to 40% of Americans are
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I mean, so what, when did that, it wasn't always like that.
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If you, you highlight all this research going back to the early 20th centuries where it was
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So if we go back, so the data, the best data that we have go back to the early 1960s.
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Those are from large scale surveys conducted by the U.S. Centers for Disease Control.
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And before that, the data gets increasingly sparse.
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But we do have data going back to the late 1800s, early 1900s that paint a very different picture
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So there was a survey conducted among white male Civil War veterans who were middle-aged
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And what they found at that time is that fewer than one out of 17 of those middle-aged white
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Whereas today, if we looked in middle-aged white men, it would be something almost like
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And so there's been a dramatic increase in the prevalence of obesity over time.
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And what we see is that that has happened very gradually over a very long period of time,
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but it's accelerated particularly between 1970 and 1980.
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So between 1970 and 1980, we see a kind of sharp uptick in the prevalence of obesity.
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What are the things that have changed starting in the 1970s that caused this sharp uptick?
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So it's impossible to say with complete certainty because we're looking retrospectively and a
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lot of things have changed and we're trying to figure out what is important and what's
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That said, I think we have some pretty good guesses.
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And the first place to start is that our calorie intake has increased quite substantially
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So compared to the 70s, today we eat roughly 218 calories per day more than we did.
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And it's actually, you know, that's a very simplified picture because what's really happened is that
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And that's explaining the divergence in weight that we're seeing between individuals over
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Because what you see, you know, if you're looking at the bell curve distribution of weight, what
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So in other words, it used to be that most people were clustered around a leaner distribution.
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And now we see there's this huge tail where you have 9% of Americans now have what would
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be called extreme obesity, body mass index over 40.
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So these are the people who really are at very high risk of health impairments and, you know,
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being the folks that you see in motorized wheelchairs and that sort of thing.
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It's really been this flattening out of the distribution over time.
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And yeah, so the question is, what explains that?
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And I think the answer is that we've seen profound changes in how we interact with food
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What we see over a long period of time, but particularly accelerating during that time,
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is that we've increasingly outsourced food preparation to professionals.
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So instead of cooking food at home ourselves, we are now buying industrially prepared food.
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We are now eating out a lot more at restaurants.
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We're essentially outsourcing our food prep to people who have kind of different abilities
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and different incentive structures in how they prepare that food.
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And it's also very, very convenient, which I think is important.
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And one of the things that, one of the ways in which that has expressed itself is between
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So what we see is that that increase in calorie intake, most of that can be explained by the fact
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So we're snacking more, we're eating, we're drinking more sweetened beverages between meals
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So overall, I think this paints a picture of really profound changes in how we're interacting
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with food in this country in terms of how food is prepared, how we're purchasing it, and
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One other thing that I'll mention is that smoking rates declined quite a bit since about 1970.
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And smoking, cigarette smoking, actually suppresses appetite and reduces body weight.
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And so I think one factor that probably played a role as well, in addition to all these changes
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in our food environment, is the withdrawal of that body weight suppressing effect of cigarettes.
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Because most people smoked back then, you take that away, and you're going to accelerate the fat gain.
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And also, instead of taking a smoke break, well, I'll go get a Twinkie or whatever.
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Well, and besides that, you also talk about, you highlight research how we just move less.
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We don't work as like, you know, back our great-grandparents, they were probably a farmer.
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And today, we, I mean, now we just like, a lot of us are just working from home.
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We just go from the bed to the desk in our office.
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And I think that probably played a bigger role in the changes in weight that happened over
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the first half of the 20th century compared to the last half.
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Because, I mean, by the time you get to the 70s, most people had more sedentary jobs by that time.
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But certainly, I mean, the earlier part of the 20th century, most jobs were extremely physically
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intensive, you know, not just farming, but working in factories, that most of these things
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were not mechanized, or they were only lightly mechanized.
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So, you know, if you were working on an assembly line and in a plant producing cars, or even
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just, you know, sewing clothing, or washing clothing, or, you know, almost anything that
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you can imagine was pretty physically intensive.
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And the things that we did at home were physically intensive, too.
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Most people didn't have cars for most of the first half of the 20th century.
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So you had to, you know, get around by foot, or public transit, or even on a horse.
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So just living life was more physically intensive.
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A lot of the things that we had to do manually back then are now mechanized.
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And so I think definitely physical activity is a factor, but probably more the changes
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that occurred in the first half of the 20th century, I would guess.
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So let's dig into why our brain wants us to eat more than we need.
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And you talk about, it all starts, we have this reward system in our brain that sort of
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What's going on with that reward system in our brain?
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Yeah, so let me explain what the concept of reward is first.
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Reward is essentially, food reward is the seductiveness of food.
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So food, depending on its properties, has the ability to spark the motivation to eat in us.
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So imagine you're sitting around and suddenly a pizza comes out of the oven and you smell
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it and you see it and suddenly you really want to eat that pizza, that motivation, that desire.
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So reward is that motivation, it's that desire, it's the pleasure that you get as you eat the pizza.
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And it's also the learning, and this is something that happens beneath our conscious awareness.
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We're not aware that this happens, but it's the learning that happens that causes your brain
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to decide how motivated you should be in the future for similar types of foods.
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And so essentially the brain is hardwired to learn to be motivated by specific food properties.
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So these include fat and carbohydrate, like starch and sugar, and salt, and protein, and umami,
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which is that meaty MSG soy sauce flavor that most of us are familiar with.
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And essentially we are hardwired to prefer these food properties and we will seek them out and
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we will learn over time which foods supply them.
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And the way we do that is via a neurotransmitter called dopamine.
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So when you eat, and this, you know, just in the last couple of years, this concept has
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So I'm really happy to be able to actually give more detail today, or at least a more complete
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picture today than I even could at the time that I wrote my book a couple of years ago.
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So essentially what happens is when you eat food, that food goes down into your digestive
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tract and your digestive tract through receptors in your mouth, but mostly in your small intestine
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So there are receptors that are detecting carbohydrate and fat and protein and salt and, and everything.
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And those receptors then send signals up to your brain.
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And this is all non-conscious or at least most of it's non-conscious stuff happening in your
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It sends signals up your vagus nerve, which is a information highway between your guts and
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And it sends that up and it informs your brain of the things that are in that food.
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And depending on the concentration of those things in the food determines how much dopamine
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So essentially your brain says, oh man, this pizza has tons of fat and carbohydrate and
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So I'm going to release a bunch of dopamine indicating high concentrations of those desirable
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And what that's going to do is it's going to motivate you to eat more pizza and it's going
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to set your motivational tone for the next time you encounter pizza.
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So the next time you encounter that pizza, your brain knows your brain has correlated the
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fat and starch and salt with the appearance of the pizza, with the smell of the pizza.
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So, you know, the triangular slices, the greasy box, where you ate it, who you were with, what
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the situation was, everything, those become motivational triggers.
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So then next time all you have to do is smell the pizza or see the pizza or be in the conference
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room where you normally eat pizza and that triggers the dopamine again and that gets your
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So that triggers, you know, another way of saying that is that you experience a craving.
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Once that dopamine hits because it was triggered by that cue that your brain had previously associated
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with carbohydrate and salt and fat, once that cue is experienced by your brain, then it triggers
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So that's basically how your brain learns to motivate you to eat food properties that were
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Because you have to remember these food properties to our distant ancestors, hunter-gatherers would
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have been extremely critical for them to obtain in a natural environment because most of them
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are supplying the calories that they need to fuel their bodies, and then others are supplying
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critical nutrients that are scarce in natural, unrefined plant foods like salt.
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You know, salt is not something you can just get very easily by going out and eating random,
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Salt is something that you need to kind of seek out either through seawater or mineral deposits
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or different cultures had different ways of getting it.
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But, you know, as mammals that sweat, we actually lose a lot of salt for, you know, a mammal.
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And that presumably explains why salt, sodium chloride is literally the only, you know,
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micronutrient, that is to say, vitamin and mineral that we can actually taste in our food.
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So just to recap here, there's particular foods, fatty foods, sugary, salty, umami foods.
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Back then, those were essential for our survival.
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Today, and so our brain, as a consequence, has this system in place where dopamine is released
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so that whenever we encounter these foods, we learn that, okay, we should want this.
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And so every time we see it, we have that desire, that craving.
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I think it's important to think, like, oftentimes people think of dopamine as the pleasure neurotransmitter,
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You can, like, eat something and, like, not really like it, but you can still want it.
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Like, you might not like the drug, but it causes that dopamine, so it makes you want to
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So this idea that dopamine is the pleasure chemical is an idea that originated in the
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It was a hypothesis that was proposed decades ago and quickly refuted, essentially.
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But it got, it kind of, like, dug in its heels in the popular mind, and it's been self-sustaining
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So you see this claim a lot in the popular press, but really the evidence doesn't support it.
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It's what causes you to want things at a really visceral level, you know.
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It's not the abstract wanting, it's the really visceral craving-type wanting that dopamine
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And it also mediates that learning that teaches your brain how to crave in the future.
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And I want to mention, you know, while we're on this topic, I want to mention that, as I
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said, the concentration of these dopamine-stimulating nutrients determines our motivation levels and
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how strong our cravings are, and also when you put them in combination.
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So when you mix the fat with salt or you mix the fat with sugar, that's a lot more tempting
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So think about, like, eating a bowl of ice cream, think about you subtract the sugar, or
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That's not nearly as seductive as eating ice cream itself, which has the sugar and the fat.
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And so today, essentially, through technology and affluence, we have refined the art or the
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skill of, you know, refining these dopamine-stimulating nutrients to their utmost levels of purity and
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mixing them together in ways that maximally stimulate our dopamine and create really strong
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motivational drives, really strong cravings to eat those foods that are probably stronger than
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anything our ancestors experienced eating whole natural foods found in their environment.
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So I think, essentially, we have this situation where these foods that we've created are just
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too good at doing what they're trying to do, and that's creating these negative consequences for us
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in the form of overeating and eating less nutritious foods.
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All right. So, yeah. So, like, that's the first problem there with how today's foods, like,
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basically hijacks our reward system. I think you gave the example, like, the Dorito is, like,
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the perfect combination of fat, carb, umami, and you eat one, and then you're eating the whole bag
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because it's just that perfect combination of fat, carbs, and savoriness.
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Yeah. I don't think I use that specific example in my book, but I think that is a relevant example.
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Absolutely. If you deconstruct what a Dorito is, it's concentrated carbohydrate plus fat plus salt,
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and then you have these other, you know, seductive flavorings on it as well that may contribute.
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And, you know, a Dorito is very calorie-dense. The thing that affects calorie density the most is the
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water content of foods. So, we think about an apple, it's, like, 80 plus percent water. We think
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about a steak, it's, like, 75 percent water. Dorito has almost no water, right? And so, that's a very
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calorie-dense food that is delivering this really concentrated combination of dopamine-stimulating
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nutrients to your brain. But I think the one that takes the cake is actually chocolate. So, chocolate,
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of course, contains very little water also. So, it's very concentrated, high in fat, high in sugar.
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But the thing that puts it over the edge is it actually contains a habit-forming drug called
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theobromine. Theobromine is similar to caffeine in that it's this, you know, mild habit-forming drug.
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But, you know, that plugs right into the dopamine system too. So, when you get this really concentrated
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combination of fat plus sugar and then you add a habit-forming drug on top of it, you've got a
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really powerful combination. And I think that explains why in studies they find that chocolate
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is the number one most craved food among the general population, but particularly among women.
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All right. So, we've got really palatable food. And you've highlighted these studies that show that
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food palatability or how tasty a food is, it has this combination of fat. That can affect whether we
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seek it out. And I think you talk about this experiment where when people are given unpalatable
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food. So, there's like this experiment done like in the 60s, I think, where there's like this machine
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where it put out this, like, I don't know, it's basically like soiling green, right? Just like
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this nutrition shake. And you could take as much as you want, but it had no flavor, but it had the
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perfect combination of fats, proteins, carbs that you needed, but it wasn't good. And people really
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didn't, they just drank as much as they needed and that was it. They didn't really, they didn't
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Yeah, absolutely. This is, it's a pretty crazy experiment. Yeah, they had people in a hospital
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that were inpatients for various reasons. And like you said, they gave them access to this machine
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that dispensed, I think it was 7.4 milliliters of this bland liquid formula is what they called it.
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Every time they pressed a button and it just dispensed it through a straw into their mouths.
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And so, they could, you know, anytime they wanted to just grab this thing, press the button,
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put the straw in the mouth and they got 7.4 mils. And yeah, so essentially you're stripping
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everything pleasurable away from the eating process. And what they found was really interestingly,
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people who were lean actually continued to eat their usual number of calories. So,
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they continued to eat their maintenance calorie intake and their weight didn't change. People who
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had obesity, their calorie intake dropped dramatically. And as you said, they were not
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asked to reduce their calorie intake. They were just given the system and said, eat as much as you'd
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like, however you need to feel full. And they, their calorie intake plummeted and they started
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rapidly losing weight. And they saw this across several individuals and then it was replicated
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by a later study as well. And yeah, so I mean, I think that just goes to show how much these
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properties, these food properties contribute to our eating behavior. And there's plenty of other
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research that supported that too. So, you know, there are randomized controlled trials, which is a
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particularly rigorous type of study design where they give people different foods with different
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types of flavorings, some of which are intended to taste good. And some of which are intended to
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taste a little weird. And, you know, unsurprisingly, this is kind of common sense, but people ate more of
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the foods that tasted good. And I should specify when you only gave them that versus only the other type
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of food, they ate more total calories of the good tasting food. And these foods were nutritionally
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identical. So, we're talking about literally just using different flavoring agents on the same
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sandwich. So, the flavor itself, how much, how much you enjoy it, how much reward value it has, how seductive
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it is, is a way that I like to put it, really does impact your food intake. And if we look across
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typical diets, you can see that variation in how good people report the food tasting
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has a large correlation with how much they eat at each meal.
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We're going to take a quick break for your words from our sponsors.
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And now back to the show. All right. So, not only is food today, the processed food,
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it's designed, I mean, it's designed to be more rewarding. So, we eat more of it and our brain wants
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that. So, that's one thing going against us. But another thing that's different about today's food
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environment compared to, say, 50, 60, 100 years, 1,000 years ago, that we have, there's more variety
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of food. And that's another factor. I think, what role does variety play in the neuroscience of eating?
00:23:49.660
Yeah, absolutely. So, one of the earliest things that alerted me to this was this really cool study.
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I think Barbara Rolls was involved in this. At least, I think this study is really cool because I learned
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something. But they had mice in different cages, or I think rats in different cages. And they were
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giving them just regular rat chow. But what they would do is they would put, in addition to that
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rat chow, they would put different tasty foods in to these rats' cages. So, I don't remember exactly
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what they were, but it was like cookies and sausages and some other tasty food. And they would put them in
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one at a time. So, if you just put cookies in, they would eat more and they would gain a certain
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amount of weight. But if you put all three of these different types of tasty foods in at the same
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time, so the cookies and the sausages and the whatever else it was, crackers, then they would
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gain a lot more weight than if you had just put one food in. Even though, you know, the one food is
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already quite unhealthy. It's already calorie dense. It should be perfectly fattening. So, it really was
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the variety per se that was having a big impact on how much they were eating and how much weight they
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were gaining. And to this day, the most effective way to fatten a wide variety of non-human species
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is to put a variety of tasty human junk foods in their cage and let them eat as much as they want.
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Literally, human grocery store food, the types that most of us would recognize as unhealthy,
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is the most fattening food in the world to a wide variety of non-human species. And so, like,
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I think it's pretty, I think that is a pretty good piece of evidence that it's probably a big factor
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in fattening humans too. So, you can, you know, just to expand on this a little bit, you can take
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rats, you can put them on a high-fat diet, they'll gain a certain amount of weight. You can put them
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on a high-sugar diet, they may or may not gain weight depending on the study. But, and, you know,
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you can even compare, you can combine fat and sugar and they'll gain more weight than just the fat alone.
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But none of those diets even comes close to human junk food, to giving them access to a variety of human
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tasty junk foods. It blows away any kind of macronutrient composition that you can put into
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a rat pellet. So, it's really, it's about way more than just the nutrient composition. It's really about
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the presentation and how seductive that food is.
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And the research shows that the same thing happens with humans, right?
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Yeah, yeah, absolutely. So, yeah, so it does work on humans. And this has been demonstrated in a
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number of studies. I think Barbara Rolls is the researcher who spearheaded a lot of those.
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And essentially, if you put people in a situation where they can eat foods, again, you can even do
00:26:51.640
this with nutritionally identical foods where you're only changing the flavoring. People will eat more
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if you have a variety of different flavors than if there's only one flavor, even again, if it's
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nutritionally identical. And so, we call this the buffet effect. When you go into a buffet, like most people
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have had this experience where you go into a buffet and you end up just eating way more food than you
00:27:16.700
think you should. And that happens particularly more at buffets than in other settings. That's been my
00:27:23.060
experience. And I think that's been a lot of other people's experience. And the reason is that
00:27:27.980
incredible food variety. Our brains essentially are designed, for whatever reason, to have this thing
00:27:35.480
called sensory specific satiety, which means that we get satiated on a specific type of flavor profile,
00:27:44.300
but not necessarily on other types of flavor profiles. So, if you have your steak, you might
00:27:49.820
not want any more steak, or you might not want any more meat in general, but that doesn't stop you from
00:27:56.260
wanting more cake. Or if you have a bunch of cake, you might not want any more cake, you might not want
00:28:02.560
cookies, but maybe you still want steak. So, that's called sensory specific satiety.
00:28:08.280
And that explains, I think, goes a long way toward explaining the impact of food variety on food
00:28:14.140
intake and body fatness. I think we've all experienced that, the buffet effect. You just
00:28:18.560
feel gross and you're like, no, I got to try that thing because it's different. Or like, yeah, the
00:28:23.800
dessert. You've eaten a big meal like Thanksgiving, right? So, there's a lot of variety at Thanksgiving.
00:28:28.160
I mean, you're full. But then like the pie comes around like, well, I got room for pie, even though
00:28:35.380
Exactly. I mean, I think this is a really great example of how our food intake is not just determined
00:28:41.080
by our nutritional needs. It's not just determined by the nutritional composition of the food,
00:28:49.000
or the calorie value of the food, or just hunger in general. You know, a lot of people really focus on
00:28:55.840
hunger as a determinant of our food intake and body fatness and weight loss. And it is important,
00:29:02.260
don't get me wrong. But hunger is not the big picture. It's, excuse me, it's not the only part
00:29:07.680
of the picture. So, yeah, think about you're at a restaurant and you've just had a meal of you had a
00:29:14.240
steak and a potato and a salad, and you're full. You've eaten already probably more calories than you
00:29:19.900
needed to eat at that meal. You're totally full. If someone put another piece of steak and another
00:29:26.500
potato in front of you, you wouldn't touch it. You wouldn't want to touch it. Yet, the waiter comes
00:29:32.260
around with a dessert menu, and suddenly you're ready to eat a piece of cake, or you're ready to
00:29:38.580
eat, you know, a brownie and ice cream or whatever it is. And that's because of this sensory-specific
00:29:45.860
satiety, you're not full on cake and brownies, you're full on steak and potatoes. And also,
00:29:52.540
of course, you know, these are very, very seductive foods. Desserts are very, very seductive foods that
00:29:59.720
really spike a lot of dopamine. All right. So, we got two things. We talked about two things,
00:30:04.460
our modern food system. Calorically dense, high reward food, a variety of it. And the other thing
00:30:09.920
that's changed compared to, say, our ancestors is that food now is readily available. It's easy to
00:30:14.620
access. All this stuff is easy to access. You know, before, if you wanted to get honey,
00:30:18.940
you'd have to, like, find a beehive and then stick your hand in a bunch of angry bees and get stung.
00:30:24.780
Today, like, I can just drive, I could walk over to Quick Trip and get a taquito and pay just,
00:30:29.900
like, a buck fifty for it. Absolutely. Yeah. And I think that is especially apparent if we're
00:30:35.480
looking over very long timelines of human history, like what you're talking about. If we're,
00:30:40.820
if you're a hunter-gatherer, you have to put in a tremendous amount of effort to get your food.
00:30:46.080
That is literally your job, getting and preparing food. That is what you spend hours on every day.
00:30:52.080
And it requires a lot of time and also a lot of effort to make that happen. And that's what our
00:30:58.200
motivational systems in our brain are tuned to. Our brain is calibrated to create enough motivation
00:31:05.160
to make you walk or jog five to eight miles a day, climb up trees, get stung by bees to meet your
00:31:13.420
calorie needs. That is what your brain is calibrated toward to in terms of generating motivation to get
00:31:20.760
food. But today, the effort barrier is so low, but we still have that same eating drive. And so, you know,
00:31:29.920
something like what we call gluttony today, I think is a really instructive example. We have a,
00:31:36.620
you know, I can't speak for all cultures, but at least in prevailing Western culture, we have this
00:31:42.180
negative judgment around gluttony, this word gluttony, you know, overeating. This is something
00:31:48.500
that we think is bad and we try not to do it very much. You know, we feel guilty about it. But if you go
00:31:54.260
back to hunter-gatherers, there's no such thing as gluttony. Like for them, eating as much as possible
00:32:01.260
is awesome because it's really hard to get that food. So when you get the opportunity to get a
00:32:06.600
really easy win and eating, you know, tons of honey or tons of oranges or tons of fatty meat,
00:32:12.840
you're going to take it and that's good. There's no downside because you're making up for other times
00:32:19.040
when you might not get as much food or when it might be harder to get food. So like this
00:32:24.180
idea of gluttony, I think really highlights this disparity between how our brains are set up and
00:32:31.580
how our modern food environment interacts with us. Like that's essentially us trying to culturally
00:32:36.860
protect ourselves against this issue that we're faced with. So yeah. So I think that today, you know,
00:32:44.700
it's obvious to anyone, I think you walk into a grocery store and there are many options for food
00:32:51.000
that you really have to do little or no work to consume. We eat out way more than we ever have in
00:32:58.240
human history. In the United States today, we spend about half of our disposable, half of our food
00:33:07.940
related expenditures is on food eaten away from home, like restaurant food, fast food. Whereas
00:33:14.280
we only spent about a 10th of our food related expenditures on food away from home back 140
00:33:22.540
years ago. And we have data going back that far and that's what it suggests. So there's been profound
00:33:30.000
changes in the convenience of food in this country. And essentially your brain, whenever you're thinking of
00:33:36.280
doing anything, whether it's shopping or negotiating for a job or making food decisions, your brain's
00:33:43.380
always doing cost benefit analysis. So it's saying, what is the benefit of this food in terms of its,
00:33:50.520
you know, calories and how seductive it is? And what are the costs in terms of how hard I have to work
00:33:56.180
for it? How much money does it cost? And how much time is it going to take me to do this? And essentially
00:34:03.500
the costs of food in terms of, again, the money and the time and the effort cost have gone way down
00:34:11.740
over the course of human history, but particularly over the last century. I mean, food is historically
00:34:17.980
cheap in the United States. We, we like to complain about the cost of food, but it's literally cheaper
00:34:23.800
than it's ever been in all of human history. We spend about 10% of our disposable income on food today.
00:34:29.940
So I think that all of the downsides, all the costs of eating that we would have experienced
00:34:37.520
historically have been minimized to an extreme degree. And there's benefits to this. You know,
00:34:42.320
there's way less starvation happening in the United States than there was a hundred, 200,
00:34:47.640
300 years ago. And that's a wonderful thing. So I don't want to present this as it's all a bad
00:34:54.600
thing, but there have been costs. And one of those costs is obesity.
00:35:00.340
Well, it sounds like just from understanding the rewards from our brain and like the things that
00:35:03.760
influence it. So the, the palatability of the food, the variety of it, the cost of it. I mean,
00:35:09.240
from there people can, there's insights there on how you can control your eating. So you're not
00:35:13.440
consuming as many calories. And it sounds like, you know, don't buy the cookies and potato chips,
00:35:17.940
stick to like basic foods like oatmeal, rice, meat, eggs, don't have a huge variety of, I mean,
00:35:25.540
variety of bad food and then make it like, keep the, make it easy to eat the good food and harder
00:35:30.540
to eat the bad food. Absolutely. Yeah. And some of this stuff that we're talking about boils down
00:35:36.020
to pretty simple principles that aren't going to, you know, be a big shocker to anybody like eat
00:35:41.160
simple on less processed foods. But I think, you know, there are some things that are a little bit
00:35:47.840
more counterintuitive to people. Like, I think people are used to thinking that their food has
00:35:55.180
to be delicious every time. And I think that that is an idea that's kind of been drilled into us by
00:36:02.960
diet marketing. Like this, every diet, no, what diet is going to say, Hey, this is, you know,
00:36:10.280
this is a bland diet. No diet is going to say that they're all going to say, you're going to be
00:36:14.640
eating the most delicious food you've ever eaten in your life. And you're going to be losing weight.
00:36:19.020
You know, it's part of the sales strategy, but the truth is that that deliciousness itself is
00:36:24.700
one of the things that is holding you back from eating a more appropriate number of calories for
00:36:31.240
your weight loss goal. And so that is one thing that I think is a little more counterintuitive. And
00:36:37.140
of course we have, the diet has to be satisfying enough that you stick to it. I think, you know,
00:36:42.600
you don't want to eat a diet that just tastes bad. You're not going to stick with it. But I think we
00:36:46.660
can eat things that are simple and satisfying that are more like what our distant ancestors used to
00:36:51.800
eat. Just simpler things like, you know, simply prepared meats and vegetables and nuts and fresh
00:37:01.460
whole fruits and limiting added fats, limiting added sugars and other things that are very concentrated
00:37:08.400
dopamine stimulating nutrients. And to this, I was going to say to this idea of, you know,
00:37:13.880
your food doesn't have to be delicious all the time. You highlight this tribe, the Kung San.
00:37:19.380
I think they're in the Kalahari Desert. And you point out that, you know, they occasionally they
00:37:24.740
get some honey, they get a truffle, which they just, they gorge on. But it says, but due to the
00:37:29.800
limitations of living in a natural environment, they ate certain other foods daily without much
00:37:34.580
enthusiasm. It's just like, yeah, it's just fuel. Yeah, absolutely. And that's what you, that's
00:37:40.500
what you see in hunter gatherer cultures. Like I think most people in, you know, cultures like ours
00:37:49.840
are accustomed to having their palates entertained with everything that crosses their lips. But I think
00:37:55.760
most of us would be severely disappointed by the diets that hunter gatherers eat. I mean, if you
00:38:02.080
actually really look at what hunter gatherers eat, and again, this is what all of us ate prior to say
00:38:08.760
12,000 years ago, they're, you know, they didn't have ovens with for controlled temperature baking and
00:38:15.980
roasting. They didn't have, they weren't sauteing onions. They didn't have sugar and white flour and
00:38:22.420
added fats. At least most of them didn't have added fats. And so, you know, we're talking about taking a
00:38:29.440
piece of meat and throwing it on the fire with no salt on it or burying it in, you know, in the sand
00:38:35.700
next to the fire. We're talking about eating fresh fruit. We're talking about eating plain roasted
00:38:41.280
nuts with nothing on them. We're talking about eating tubers that had weird off flavors. Like
00:38:47.820
sometimes they were bitter. Sometimes they had other, you know, flavors that we wouldn't necessarily
00:38:53.080
enjoy. Tons of fiber sometimes in these tubers so much that you might have to spit out a lot of it
00:38:59.400
as you're eating it. Some of the fruits they ate were not very sweet. Depends on the fruit. Some of
00:39:04.840
them were sweet. Some of them weren't, but some of them were not very sweet. And so you're eating this
00:39:09.840
like, you know, kind of tart, not very sweet, fibrous fruit. So like, that's a lot of what they were
00:39:16.480
eating day in, day out. And so that's not to say that they never had foods that were tasty. Again,
00:39:21.680
sometimes they did, but I think that overall the diet was a lot less seductive, a lot less
00:39:30.120
entertaining to the palate than what we eat today. And that's not surprising. Today we have incredible
00:39:35.100
control over what passes our lips. You know, our distant ancestors, they ate what was available or
00:39:40.480
what grew well in their area. But today we can refine things. We can extract the dopamine stimulating
00:39:48.100
sugar or MSG or, you know, starch or fat or whatever it is from those whole natural foods,
00:39:56.440
concentrate them and combine them into these really delectable kind of art forms for the primitive
00:40:04.520
parts of our brain that judge these things. And so it's just a very, very, very different picture
00:40:12.640
All right. So we've talked about the food environment and how it is designed, basically.
00:40:17.320
It's like there's an evolutionary mismatch. Like our brain wants these things at certain
00:40:20.760
time in human history, that was good. But today it's just too abundant and it causes us to overeat
00:40:26.460
and we get fat. Then you also in the book talk about another part that's driving us to feel hungry or
00:40:32.960
not. And it's this hormone called leptin. I'm sure people who are listening to the show probably
00:40:38.140
heard of leptin. They've read some stuff about health and fitness online. But can you walk us
00:40:43.460
through like what is leptin and what role does it play in our desire to eat?
00:40:48.980
Yeah. So essentially leptin is a key piece in the system that regulates body fatness in humans.
00:40:56.260
And the way that system works is that I'll start with an analogy. So if you imagine a thermostat,
00:41:02.940
thermostat measures the temperature in your house. And then whenever the temperature deviates
00:41:08.200
from whatever the set temperature is, it will either kick on heat or it will kick on
00:41:13.800
air conditioning to bring it back to that set temperature. And that's called a negative feedback
00:41:19.060
system or you call it homeostatic regulation. And these things are pervasive both in engineering
00:41:25.360
and in biology. So there's tons of things like this in the human body. For example,
00:41:30.400
temperature regulation is a great example. So the way the system works for regulating body fat
00:41:38.400
is that you have this hormone leptin that is produced by your fat tissue in proportion to its
00:41:45.160
size. So the more fat you have, the more leptin gets produced. That enters your bloodstream and it's
00:41:51.880
detected by parts of your brain. And those parts of your brain essentially compare it to
00:42:00.260
what they think it should be. And if your body fat level starts to drop, let's say you're going on a
00:42:08.580
diet and your body fat level starts to drop, the leptin goes down. Your brain is informed of the fact
00:42:16.660
that your body fat is going down via declining leptin levels. And then your brain kicks in the
00:42:22.640
suite of responses to bring the fat back. So your brain makes you hungrier. Your brain makes you crave
00:42:27.860
foods more. Your attention is shifted to pay more attention to foods. You might find yourself having
00:42:34.720
a harder time walking by the cookie aisle. And at the same time, if you lose enough weight,
00:42:42.180
your metabolic rate also starts to decline. So your brain actually starts to shut down
00:42:47.700
your metabolic rate a little bit. Essentially, what your brain is trying to do is bring in more calories
00:42:53.100
and reduce the number of calories leaving so that you're able to squirrel away more into your fat
00:42:59.380
mass to bring that back to where it was. And the thing that really sucks about this system is that
00:43:05.040
it will actually regulate, it will defend against fat loss even in people who have obesity. So even in
00:43:12.500
someone who really carries more fat than is healthy, their brain is still going to defend their current
00:43:19.960
level of body fatness. So when your leptin level starts to drop, your brain is going to say,
00:43:24.280
no, I don't like this. And it's going to kick in that same starvation response because that's
00:43:30.040
exactly what I just described. It's literally a starvation response. It's going to kick in the
00:43:35.000
same starvation response that it would kick in if a lean person started to lose weight. So someone who
00:43:40.940
is actually really starving, like their body fat stores were depleted and they're actually under real
00:43:46.880
physiological threat, they're going to kick in a certain suite of responses. And of course,
00:43:52.340
this is all non-conscious. It's happening from non-conscious parts of their brain. They're
00:43:56.840
going to kick in this protective starvation response. Someone with obesity has the same thing
00:44:03.020
when they start to lose weight. So that's really something that's really challenging about how human
00:44:09.920
biology is set up. And so when you look at randomized controlled trials, again, that's this rigorous type
00:44:15.740
of study of different weight loss approaches. What we see generally is that people can lose weight on
00:44:22.820
almost any diet, but also on any diet, people will start to rebound after their period of maximum weight
00:44:31.980
loss. So generally in these studies, you see maximum weight loss around six months, and then people will
00:44:37.100
start to regain weight. And essentially what's happening, or I don't want to say this is the entire
00:44:42.320
picture, but a key part of what's happening is that people are losing the battle against their own
00:44:48.960
non-conscious brain that is trying to bring that fat back. They're losing the battle against these
00:44:55.680
brain regions that are actively undermining them and creating a struggle for them where they're having
00:45:03.580
to fight their own impulses to maintain that weight loss.
00:45:07.080
No, I think everyone who's tried to lose weight of experience, they lose the weight and then they
00:45:11.680
gain it back. And we've seen this dramatically on shows like Biggest Loser, right? People lose lots
00:45:16.480
of weight and then you follow up with them a year later and they've gained it all back. And I guess
00:45:21.260
that's leptin. There's no leptin there. And their brain's like, you got to get, you guys get back to
00:45:26.120
where you were. And so you start eating more and that's what happens.
00:45:30.800
Absolutely. And it's like stretching a rubber band. The harder you stretch it, the more resistance you
00:45:35.960
feel. And so for someone who's really lost a lot of weight, like people on The Biggest Loser,
00:45:40.980
they're going to have an extreme starvation response that is driving them back toward weight
00:45:46.040
gain. So, and as you said, you know, you follow up with these people a year or two later, most of
00:45:51.420
them have regained most of their weight. And, you know, I don't want to, a lot of times this comes
00:45:56.660
across as really negative and hopeless. I don't want to come across that way. I don't think that it is
00:46:02.620
hopeless to try to lose weight. But I do think that there are challenges that are because of how
00:46:09.080
the human brain and the human body is constructed. And I think it's really helpful for people to
00:46:14.100
understand those challenges because then they know what they're going to be up against. They're
00:46:18.360
prepared. They're not going to be, feel like a failure when they, when they hit those barriers
00:46:23.360
and maybe they'll have better tools to help overcome those barriers. And also, I think it
00:46:28.060
helps people not be as judgmental. Like if it were easy to lose weight, if we didn't have these
00:46:33.880
barriers, probably there wouldn't be very many people with obesity, right? I mean, this, these are
00:46:39.620
the things that are making it difficult and undermining people's well-intentioned efforts to lose weight.
00:46:47.540
Well, are there any insights from neuroscience that can help people manage that, that leptin battle?
00:46:54.040
I mean, is it just a matter of, okay, you know, it's going to happen. So you need to have a plan
00:46:57.680
and maybe you just have that plan and you stick to it, even though your body is like, no, eat the
00:47:03.200
cheesecake. Yeah. So I think, so there are a couple of different ways you can approach it. And these are,
00:47:11.460
you know, the first one I'm going to explain is a little bit of a caricature, but I'm just doing it to
00:47:16.140
prove a point. There's the kind of pure willpower approach where you say, Hey, I'm going to keep
00:47:22.520
eating the same foods that I've always been eating. Maybe my diet started off unhealthy. I'm
00:47:28.080
going to keep eating the cookies and the cake and the fried chicken. And I'm going to keep eating all
00:47:34.860
that stuff, but I'm just going to use portion control. So I'm going to try to eat half as much
00:47:39.340
as what I used to eat. And I think that's the situation where you're really going to be setting
00:47:45.440
yourself up for struggle, because when you do that, your brain doesn't like it. I mean,
00:47:52.760
the amount you were eating of those foods before was the amount that your brain was intuitively
00:47:58.260
telling you to eat, right? Because the way we eat is we sit down and we keep eating until we're full
00:48:03.760
and then we stop eating. That's the natural way of interacting with food for a human. And so you're
00:48:10.060
forcing yourself to not indulge your impulse to eat until you're full. And so you're setting up a
00:48:17.160
struggle between your, you know, higher order cognitive willpower parts of your brain and the
00:48:24.840
lower order, you know, intuitive impulsive parts of your brain. And that's a struggle that most people
00:48:30.200
just can't win in the longterm. Some people can, you know, this, it does work for some people and
00:48:37.600
they can do it. You know, some people just to have an iron will, but I don't think most people do.
00:48:43.480
And I don't think most people should expect themselves to, because it's just not really how
00:48:48.080
the human brain is set up. So I think a better way is to set up the situation so that you don't
00:48:55.400
have to exert all that willpower. So you set up the situation in such a way that you're actually
00:49:00.240
trying to change those impulses. You're trying to directly change how you're interacting with those
00:49:07.380
non-conscious part of the brain that are generating those impulses. And so that's just to give you a
00:49:13.020
couple of examples that are particularly important, changing your food environment so that you're not
00:49:18.060
feeding your brain food cues all the time. So again, when you see these, when your brain gets these
00:49:23.740
cues, like the sight of food or the smell of food, that triggers dopamine release, that triggers your
00:49:29.220
motivation to eat. So if you eliminate those cues, you're going to reduce your motivation to eat
00:49:36.880
more than you want to and things that you don't want to. It's the same thing as someone who's
00:49:41.680
trying to quit smoking. You don't leave packs of cigarettes hanging around the house. You don't go
00:49:45.960
to the places you used to smoke. You don't hang out with people who are smoking. You're trying to
00:49:50.340
eliminate those cues that are going to cause you to relapse into that dopamine-driven behavior.
00:49:56.600
So that's one thing. And then another thing is to eat foods that create greater levels of
00:50:03.000
satiety or fullness per calorie in the parts of your brain that process fullness, the feeling of
00:50:10.080
fullness. And the feeling of fullness that you feel is only loosely connected to the number of
00:50:17.040
calories you eat, but it's more tightly connected to food properties like how calorie-dense the food
00:50:23.440
is. In other words, how many calories per gram or per volume. So if you have food that is very,
00:50:31.080
very calorie-dense, like chocolate or bread is pretty calorie-dense, for the same number of
00:50:39.760
calories, it doesn't fill your stomach up very much. So 100 calories worth of those foods is not
00:50:45.140
very much volume. Whereas if you're eating a bowl of oatmeal or a piece of fresh fruit or a piece of
00:50:50.680
fresh meat, that is mostly water. So it actually, per calorie, fills your stomach up more, and that
00:50:56.600
sends signals up to your brain that actually makes you feel full. And so you end up feeling full having
00:51:05.040
consumed fewer calories. And again, since we sit down and just keep eating until we feel full, that's
00:51:11.160
the intuitive, natural way of interacting with food. You could eat half as many calories and feel just
00:51:18.000
satisfied if you're eating unrefined water-rich foods than versus if you were eating processed
00:51:26.720
calorie-dense foods. So that's another thing. So it's not just the calorie density, it's also the
00:51:32.020
protein content that makes you feel more full per calorie. It's the palatability, so how delicious it
00:51:39.080
tastes. The more delicious the food it is, the less filling it is per calorie. And the fiber content,
00:51:45.740
the more fiber is more filling. So just setting up your food environment, setting up the types of
00:51:52.680
foods that you're going to eat at a meal can actually help control those impulses in the first
00:51:58.000
place. So instead of struggling against hunger and struggling against cravings, you're actually
00:52:03.360
nipping those in the bud beforehand. So you're not having to day after day after day fight yourself
00:52:13.060
Well, two other factors you highlight about modern life that causes us to overeat is we don't sleep
00:52:19.840
enough. We're bad sleepers and we're stressed out. So what role does sleep and stress play in
00:52:27.340
Yeah. So sleep, there have been some studies. Sleep is pretty interesting. So you look at the
00:52:32.680
observational studies. So these are ones that just say, we're going to look at a bunch of people,
00:52:37.460
we're going to see how much they sleep and how much they weigh and how their weight changes over time.
00:52:41.960
And then we're going to see if there's any relationship between those two things.
00:52:46.280
And those studies find that actually sleep, short sleep is really well correlated with weight gain
00:52:53.020
over time. So people who sleep less than six or seven hours a night tend to gain more weight than
00:52:59.100
people who don't. And it's pretty big correlation. Of course, you might say, well, that could be
00:53:04.560
confounded. It's observational. What does it really mean? So there have also been these short-term
00:53:10.760
randomized controlled trials. Again, that's a really rigorous study design where they actually
00:53:16.200
restrict people's sleep in one group and not in another group. And then they compare their calorie
00:53:21.440
intake. And what they find is that when you restrict people's sleep, they eat more. And it's
00:53:28.040
pretty significant effect. I don't remember exactly what it was, but I get into detail in my book. It's
00:53:33.760
like 150 calories a day, something roughly on that order. And you're sleeping less. You're actually
00:53:43.300
burning a little bit extra energy too, but not enough to make up for the extra food that you eat.
00:53:48.740
And basically what it looks like is that it kind of turns on your body's, your brain's appetite
00:53:54.040
systems. When you put people in a fMRI, which is a kind of brain scan, and you look at their brain
00:54:01.500
activity when they're looking at images of food, they have more activity when they haven't slept
00:54:07.060
enough. So basically their brain is getting more excited about eating food than it would if they had
00:54:14.500
slept enough. And so essentially, yeah, this paints a picture where sleep causes you to eat more or
00:54:22.860
excuse me, insufficient sleep or low quality sleep tends to cause people to eat more. I don't want to
00:54:28.500
say that the evidence is super ironclad, but I think it's, it pretty, pretty strongly suggests that
00:54:35.100
is happening at this point. And then as far as stress is concerned, there are surveys that have been
00:54:41.900
conducted by, I think the American Psychological Association that suggests that people react
00:54:47.440
really differently to stress. So I think it's roughly 45% of people report overeating when they're
00:54:54.320
stressed. And then some 30 some percent of people report actually skipping meals. And so it has this
00:55:01.080
really different effect on different people, but a lot of people do start to over consume when they're
00:55:07.520
stressed. And they particularly fall back on comfort foods, which are usually these calorie dense foods
00:55:13.520
that we would normally think of as not very healthy and pretty fattening, you know, mac and cheese and, and
00:55:25.740
So bottom line there, get better sleep, practice good sleep hygiene, that can help, won't hurt, and then manage
00:55:31.520
manage stress in other ways besides eating food.
00:55:36.820
Well, Stefan, this has been a great conversation. Is there some place people can go to learn more
00:55:42.440
Yeah. So the book is available from any place that sells books. Amazon is, is an easy place to get it.
00:55:50.180
My personal website is stephanguena.com or you can, if that's too hard to spell, you can do
00:55:57.720
wholehealthsource.org. That'll take you to the same place. I haven't been really active on my website
00:56:04.180
yet, but, or lately, but I do, I am fairly active on Twitter. Although since coronavirus, I haven't
00:56:13.280
really been, had as much time to write about health and nutrition topics. But I do also want to
00:56:19.100
recommend another website called Red Pen Reviews, which is an organization that I founded along with
00:56:25.300
some other nutrition experts that posts authoritative reviews of popular health and
00:56:32.200
nutrition books. And that's at redpenreviews.org.
00:56:36.340
Fantastic. I'm going to check that out. Well, Stefan Guillenet, thanks for your time. It's been a
00:56:41.100
My guest today was Stefan Guillenet. He's the author of the book, The Hungry Brain. It's available
00:56:44.880
on amazon.com and bookstores everywhere. You can find out more information about his work at his
00:56:48.420
website, stephanguena.com. Also check out our show notes at awim.is slash hungrybrain, where you can find
00:56:54.080
links to resources, where you can delve deeper into this topic.
00:57:03.720
Well, that wraps up another edition of the AOM podcast. Check out our website at
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