Can some foods have addictive properties? We all have cravings for some things--chocolate, let's say? But can food really hijack the brain much as happens with classic substances of abuse? And are foods engineered by the food industry in ways that trigger addictive like reactions in the brain? Such are the questions being asked by Dr. Ashley Gearhardt. She is an associate professor of psychology and the clinical science area at the University of Michigan and a leading researcher in the field of food and the brain, food, and addiction in particular.
About Ashley Gearhardt
Ashley Gearhardt received her Ph.D. In clinical psychology at Yale University with training on the underpinnings of both excess food and alcohol consumption. Her work explores eating-related problems across the lifespan and particularly the role of food craving and liking in eating dysfunction. She also investigates the role of addictive processes and compulsive overeating and is director of the Food Addiction Science and Treatment Laboratory at the University of Michigan.
What interested you in these topics and how you got going on this area?
Yeah, absolutely. For me, it was really a perfect storm of scientific experiences and exposures that lead me to really pursue this line of research. And at the time I was in grad school, I was initially studying traditional addictive substances like alcohol and how we responded to that. But at that time, not only was there this major global obesity epidemic, but there was all this research coming out from the neuroimaging world. They were finding that the way that the brain responded to really highly processed, highly rewarding foods really seemed to engage the circuitry in the brain that goes awry in addiction. And then Nicola Vena Bart Hobos group at Princeton, they were publishing this beautiful research in animal models showing that really being exposed to a lot of sugar and then having it removed from the diet could trigger all the classic signs that we think of when we think of addiction. The rats would binge, they would go out and pursue trying to get sugar even if they were getting electrified and shocked. And they would go through withdrawal when sugar was taken away from their diet, even if they had other foods and chow available. So this really got me inspired to think about where does the boundary lie here? What does it mean if these highly processed junk foods that have become so common in our world truly are addictive? Where's the boundary? What do we know and how do we figure it?
Individuals who are listening to this are probably wondering what it means to have food having this impact on one's brain. And let's begin by talking about the Yale Food Addiction Scale, which you developed and has now been translated into many languages used by researchers around the world. What sort of questions does it ask people? That'll give our listeners a sense of how the addictive impact of food might actually be experienced by individuals.
Absolutely. So what we have seen--when I first started doing this work I realized that wasn't really any sort of measure or tool out there to try and identify who might be actually showing signs of addiction to these foods. And so I used the diagnostic criteria, the way we diagnose alcohol use disorder, cigarette use disorder, and I applied those to the consumption of these highly rewarding foods. And some of the behaviors that we see that people report is that they really struggle to maintain their control once they start eating some of these foods. So they'll think, okay, I'm just going to have one cookie and the next thing they know that the whole pack is gone. There are really intense cravings. I mean, we all experience cravings, but it's almost that the craving is so strong that you can't think of anything else. That person will have a strong desire and really be trying hard to cut down, but they just keep repeatedly failing. There's a tendency that even if you have some pretty significant negative consequences, health consequences, emotional consequences--you keep returning to that same dietary pattern. And so these sorts of behaviors seem to be key. And we also see that people are reporting things like withdrawal. That when they cut down on these highly processed foods try and eat healthier then they experienced a really big uptick in cravings. They experienced irritability, headaches, fatigue, and just really a struggle to maintain this healthier dietary pattern. Because the foods themselves seem to have kind of taken an oversized view in their world. They really start kind driving their eating behavior and sometimes driving their entire life.
You're talking about the kind of extreme cases where somebody might set out to eat one cookie but eats the whole package. Are there lower levels of this that may not be as clinically significant but might be important from a public health point of view? Somebody who is having two cookies rather than one or not, or having one soda rather than zero--are these same processes in effect at those levels?
Absolutely. I'm so glad you brought that up because people sometimes think of addiction as this black and white thing. You kind of either have it, or you don't. But really that's not what we see with any addiction. You know, there is this kind of the extreme tail end of people who are kind of full-blown, clinically addicted. If we think of alcohol, about 10% of people who use alcohol will get clinically addicted. In that case, we might really think about treatment and pharmacological approaches to helping them get better. But when you look at alcohol, it's one of the top leading causes of preventable death in the United States. And that's driven mostly by people who don't have a full-blown addiction to alcohol. But alcohol has enough of an addictive pull that for some people they're using it just enough that it's starting to impact their health or lead them to make unwise decisions like getting behind the wheel of a car when they really shouldn't.
And I think this is going to be even more important in the context of these highly processed foods. We see in our work that on average, the average person is experiencing at least one to two symptoms of addiction when it comes to their relationship with these highly rewarding foods. And if we think about this with food--we all have to eat. It's so in our face--these highly processed foods are always there, and it really doesn't take that much of extra consumption or an extra pull from these foods to start consuming enough extra calories that maybe you're starting to deal with health issues or gaining weight in a way that's problematic. So when I really think about this, we do need to be thoughtful about providing clinical treatment and helping people. But from a public health perspective, the biggest concern is if these foods have enough of an addictive pull, they trigger enough of a response that you really struggle to eat in moderation. That says, on a broad scale, people are struggling with their relationship with these foods in a way that increases health-related problems.
You were mentioning as you were describing the Yale food addiction scale, things that people might experience like craving and withdrawal. And I think most people are familiar with what those concepts mean. The concept of tolerance also comes up in addiction a lot. Can you explain what tolerance is and those that apply to this area?
Absolutely. My pleasure. So tolerance is when you start using an addictive substance, and your body is trying to adapt to it. You know, our bodies really want to kind of be in an even-keeled state. And so if you're taking something like alcohol and it has this big impact on your bodily systems, it kind of slows everything down. And so when you start drinking alcohol, your body tries to adapt to it by kind of speeding up before you have the alcohol. And how this impacts you over time is that initially it might've had one glass of wine and felt pretty tipsy and intoxicated. But over time, as you drink more and more, your body's adjusting more successfully. And so then you need to drink maybe the whole bottle of wine to get the same effects that you used to in the past from a much lower amount.
So this tolerance can kind of drive people to consume larger and larger quantities of food or larger and larger quantities of alcohol. And we're seeing that similar processes may be playing a role in the reward system when it comes to these highly rewarding foods. That initially, consuming a little bit of, let's say a sugar-sweetened beverage, really hits the level of reward that you're hoping for. But over time, as your body adapts, it gets used to it. It starts to prepare for it more successfully. You might need to consume rather than just a can of coke maybe you're starting to get closer and closer to a Big Gulp to get that level of reward and satisfaction that you want. And one of those things that is a little more challenging to study in the context of food is that unlike something like alcohol--that maybe people have their first drink when they're 14 or 15--with these highly processed foods were being exposed to them from the very first years of life.
So this tolerance effect may actually start to emerge in infants and young children. And it's going to be really important to try and understand on a global level as well when you're seeing these major diet shifts where all of a sudden we're going from traditional diets to a western food diet. Western diets are really very saturated with highly processed foods that are impacting the reward system in a way such that people start to expect more intensely rewarding foods and it takes larger quantities of those foods to start to get the same reward experience that they used to in the past.
These foods carry calories with them, and you can see that increasing need or desire for these foods over time creates an increased risk for obesity and diabetes. Let me ask the question about particular types of foods. Are there certain foods or constituents of foods that are most likely to trigger these effects?
Yes. So we see pretty strong evidence in this in our lab that it's really these foods that seem to have high levels of refined carbohydrates like sugar or flour or starches and high levels of fat. And from an evolutionary view, this makes a lot of sense. Our brain--the reward system of our brain--evolved at a time where food was scarce. It evolved to be sensitive to calories and to motivate us to find the foods in our environment that had the most calories. And if we think about that from early human history, that would be foods that were higher in fat like perhaps animal meats or nuts, or foods that had a high amount of naturally occurring sugar like a berry. And so our brain says, man, if it tastes something sweet or fatty, it remembers that it gives us a bigger reward response.
But what's happened is that our brain systems have stayed in this kind of "preparation for food scarcity stage" where it says: really pay attention to those foods and respond to them. But our food environment has changed so drastically. And so the food industry has become so skilled and adept at making these foods that are really dense and the amount of fat and refined carbohydrates they have. They just kind of blow out of the water the level of reward that our brain really evolved to handle. And so it is those foods that have just like a lot of sweet, a lot of fat, a lot of calories that really activate those reward systems in the brain in a way that really seems to mimic what we see with the drugs of abuse. Think of some of the top foods--things like chocolate and pizza and French fries and really sugary things like sugar-sweetened beverages where people start to show these addictive behaviors. It's not really those naturally occurring foods like fruits and vegetables and lean meats and legumes. You know, people just don't seem to show an addiction to things like kale.
How much is known about the impacts of these foods on children?
That is something that we're really diving into deeply in our lab, particularly infancy. We see that by the time a child is two, they're more likely to have a sugar-sweetened food or beverage on any given day than they are a fruit or vegetable. And when we think about this, you know, we know from other addictions that the earlier you're exposed to an addictive substance, the more vulnerable you are. And the more likely you are to develop problems with that addictive substance potentially. As I mentioned earlier, when you think of something like cigarettes or alcohol or cannabis, most people are being exposed to this in early adolescence or early adulthood. Whereas with these potentially addictive foods. The early exposure is maybe in the first year of life. And so we're just starting to really understand how that might impact the brain.
We suspect that if you're getting a lot of exposure to these potentially addictive foods, that may be impacting the reward and motivation circuitry in the brain and setting it up. So the threshold of food reward you're anticipating is more at these addictive levels, and that things like fruits that generally typically would have been rewarding, maybe just aren't sufficiently activating for these kids and really it's starting to drive a lifelong dietary preference towards these highly processed foods. We see in our research that, you know, even kids as young as eight years old are showing kind of a one or two symptoms of addiction-like eating based on the Yale food addiction scale, and this seems to predict a greater tendency towards being overweight. To consuming more junk food in the lab, and to be more prone to lose control of their eating behavior.
Are there lessons from other areas of addiction then that can be applied to the food area for either prevention treatment?
Yeah, absolutely. And I think what we've learned from the addiction world is that it's important to have good, solid empirically supported treatments. Cognitive behavioral therapy is a good one. There's really good pharmacology out there that can be considered for addiction with things like Methylnaltrexone. Even if you have excellent treatments, if this is occurring in a really toxic environment where the addictive drug is cheap and easily accessible and heavily marketed, and really societally normative, even the best treatments kind of can't compete with an environment that's putting so much pressure on the individual to be exposed to these addictive substances. And so when we look at what has been helpful on a kind of population public health level, with, for example, tobacco, things like taxation, things like reducing accessibility through vending machines, things like restricting advertising have really been successful in having an environment where it's encouraging less use of the addictive substance. And when you have that kind of environment, it really then gives the treatment a better chance of being successful. And so I think when I think about food, you know, man, the environment! And changing the environment through policy is going to give our treatments the best chance of being successful. And we have to think about that and not just focus solely on the individual. But think about the environment that they're operating in.
As this field looks forward, what do you see as interesting and important questions?
So one of the things I'm really interested in is that infancy period. What happens the very first time you have a cookie or a cake? If you're a child who's getting--in those first years of your life--a diet that's really rich and these highly processed foods, how does that set you up potentially for a lifetime of struggles? Are there things that we can tell parents that can help them set up their child with a better diet and those early, early days, um, to help them be successful? And are there ways that we can pass policy that could potentially protect children and adolescents from our kind of current toxic food environment? One of the things I'm working on in my lab is actually spending a lot of time investigating teenagers and how they might be at risk. We see that teenagers are neurobiologically very vulnerable. Their reward systems have adapted and developed more rapidly than that system of the brain that helps put the brakes on. And I think anybody who interacts with a teenager can kind of feel that sometimes--that it's all about reward and what's happening right now and not necessarily thinking about the long term consequences of it.
And the food industry is really taking advantage of this by targeting adolescents really intensely for marketing of potentially addictive foods. And some of the work that we're doing in our lab is finding out how those advertisements that teens are being exposed to for these potentially addictive foods. It's really getting in under the skin. It's really activating reward systems in the brain in a way that they may not be consciously aware of, and that is setting them up not only to eat more of these highly processed, potentially addictive foods but to be at higher risk for weight gain over time. And, when I think about this, because it seems to be a situation where it's happening unconsciously, it's happening on this biological level, just using intervention and just trying to help kids try and protect themselves from these advertisements, it isn't going to be sufficient. It's really going to be more effective to reduce the amount of these advertisements that teens are exposed to.
You were talking about the importance of early exposure to this food. What about the mother's diet during pregnancy or other the mother's or father's diets even before conception occurs? Is there any evidence on those issues?
Yes, there is this really interesting line of emerging research that suggests a role for prenatal exposure-when the mom is pregnant and is eating a diet that's rich in these highly processed foods. Based on what we've seen in animal models, there seems to be a pretty clearly impact on what kinds of foods the babies prefer and how the reward systems of the brain are set up even before the baby is born (in these animal models). If the mom has consumed a lot of these highly processed junk foods, when the baby's born, the dopamine system of the brain that's really associated with addiction and reward and motivation, it seems to be changed and altered in a way that drives these babies to have a really strong preference for junk foods themselves. And it might set these babies up not only to be more vulnerable for a preference for these junk foods but that they might also be prone later in life to be more likely to develop a preference for addictive drugs like alcohol or amphetamines. So, we think about for this kid, you know, what is the first thing they eat? But also in those early in utero periods, and what the mom's eating even before she gets pregnant may actually start to program preferences for these foods. So we just really can't start early enough trying to shape their preferences away from these potentially addictive foods.
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