Chew on This: The Science of Stress Eating

Todd Price: Welcome to Short Talks from the Hill, a research and economic impact podcast from the University of Arkansas.

My name is Todd Price.

After a stressful day, who hasn’t torn through a bag of potato chips or eaten an entire pint of ice cream? Stress eating is real. What drives us to stress eat? Is it our bodies? Our minds? Or has our culture taught us to seek comfort in unhealthy food?

Today on Short Talks, our guest is Grant Shields, an assistant professor in the Department of Psychological Science who studies the way stress affects how we think, how we make decisions and our health.

Professor Shields has recently been reviewing what we know about stress eating and what we still need to understand.

Stress eating can affect not just our personal health. It turns out stress eating may also have broader economic impacts.

Grant Shields, welcome to Short Talks, and hopefully being a guest on a podcast will not be too stressful.

Grant Shields: Thanks, Todd. It’s great to be here.

TP: Well, let’s start with a basic definition. What is stress? And are you defining stress in a way that aligns with how we define stress in everyday life?

GS: I define stress as the subjective experience that occurs when we perceive our situation, broadly defined — this can include social situation or extended in time — broadly defined to be unpredictable, uncontrollable, and presenting a real or perceived threat to the physical or social self. And a couple of other things, stress is really characterized by a specific biological response. And it is probably partially because of that response that stress does what it does to eating behavior and food choices.

TP: Let’s talk about eating in general, then. Is it fair to say that most of us, given the choice, would prefer to eat unhealthy food? And why is self-regulation so important for healthful eating?

GS: I think that there are probably some folks out there that are maybe exceptions to the norm, but by and large, I think that most of us would prefer to eat unhealthy foods. We’ve just gotten really good as a society about focusing in on those things that, throughout our evolutionary past, were most indicative of foods that would help us live longer.

And so we find things that are really easily digestible, in terms of providing quick energy to us like sugar, very hyper palatable — and the same with fat, right? Those are kind…it brings… fatty foods…bring more calories per bite than anything else. So we like both of those things, and when we put them together…Yeah, I think you would be hard pressed to find somebody that doesn’t occasionally enjoy a really nice piece of chocolate cake or something like that.

TP: Well, if we need to self-regulate and control ourselves, to be good and eat healthy, what does stress do to that self-regulation?

GS: So we can talk about self-regulation in a lot of different ways. At its core you can kind of conceptualize self-regulation as a bit of a seesaw between things that we want to do and things that we know that we should do in kind of a long-term goal directed type of way.

Stress can affect both sides of the seesaw. It can affect our reward processing, and our kind of negative emotionality. Both of those things are going to increase the “I want to do the bad thing right now” side of that seesaw. It also can affect the extent to which we can maintain our long-term goals, and perhaps even implement kind of self-regulatory control processes to override the nasty emotions that we feel.

So stress really monkeys with both sides of the equation. And it’s typically thought that it does so in a bit of the same way on either side, but typically such that it really makes that thing that we shouldn’t do look a lot more appealing.

TP: Got it. Well, does stress actually change how we taste and perceive foods.

GS: There are some studies that do suggest so, yes. That research is not entirely consistent, but by and large, yeah, it seems like stress can influence even the minimum detectable thresholds that we need to perceive something as say salty or sweet.

TP: So that would mean that we would desire that more or recognize it more. What does changing that threshold do?

GS: That’s a tough question. Without knowing a whole lot more about how temporary and transient changes in those thresholds lead to real eating behavior. It’s tough to say, that’s not my area of expertise. But I do know enough about, say, the addictions literature that when you can’t experience the same level of reward from a substance, you might be tempted to take more of a substance to experience what had been that same level of reward.

Alternatively, though, it is possible that because we really like sugar, tasting more sugar might just kind of snowball into a greater consumption of it. So, I’m really not sure one way or the other how we might expect stress to influence, say, average eating behavior and weight through that mechanism. But I think you could come up with some good arguments for either side.

TP: And what are the other important physiological and psychological factors that lead to stress eating and affect appetites when it comes to stress?

GS: Yeah, so a lot of us engage in comfort eating, maybe even intentionally. We know that the chocolate cake makes us feel better while we’re eating it, at least. It turns out, actually, if you look kind of long term, once the chocolate cake is gone it tends not to have really helped that we ate it. But we can keep eating the chocolate cake, maybe because of a cultural understanding around, “Well, I’m stressed. I feel like it’s okay to eat this thing right now.” That that could be one mechanism.

Stress also directly affects some of our physiological processes in ways that make us want food more. There’s some evidence that stress increases the hunger hormone ghrelin and cortisol, which is like commonly known as the stress hormone cortisol. That’s a misnomer in my opinion. Cortisol is a glucocorticoid. Its primary function is actually energetic. And what it does is mobilize our reserves such that our muscle and other forms of tissue have more glucose, kind of at the ready if need be, for an extended exertion. And because of that, our systems that we have in place to kind of detect those reserves start sounding alarm, saying, hey, we may need a little bit more glucose here.

TP: Is comfort eating effective. I mean, should we do it? It sounds like if we just keep doing it, and don’t stop, it will work.

GS: Can I say that I don’t occasionally comfort eat knowing what I know about the stress and eating behavior literature? Not at all. Should I comfort eat, knowing what I know about the stress and eating behavior literature? Not at all. It doesn’t seem to be effective long term, but it is very effective in the moment. So if you’re dealing with some incredibly overwhelming negative affects, maybe don’t feel too bad about eating that pint of ice cream.

But in the types of negative affect that we typically experience from a stressor, yeah, it’s probably not a good idea to eat ice cream.

TP: Which I guess goes to my next question. It’s not enough just to understand we want to eat this because we’re stressed, and this is not something we should do. Overcoming that, the sort of intellectual understanding that this is stress eating, isn’t enough to stop us typically.

GS: Yeah, at least to me.

TP: Even you. And you study this for a living.

We often think about stress as something that we suffer as individuals. Losing a job can make us stressed. An upcoming test in school can make us stressed. But there are larger events that can stress a lot of people at once. A pandemic. An economic downturn. Do we see broad changes in the way people eat when these events occur?

GS: We do. There are fewer studies on this than you might imagine. One of the only kind of national or international stressors that’s been well studied with respect to eating behavior and stress the COVID0-19 pandemic. I don’t know if you’ve heard the joke about gaining the COVID-19, but that’s basically what that literature has found: the pandemic was associated with a shift in food preferences.

People tended to eat fast food and hyper-palatable food a little bit more. Maybe that’s because they didn’t want to go to the grocery store. And that shows kind of the complexity of considering these national stressors. But yeah, at least in the situations in which it’s been studied, nations and populations tend to show the expected effects that you would think you would see from this kind of more micro lab experiment type of research.

TP: And has there been any have there been any studies that show that it actually changes consumer habits in a way that you could measure? Is it that broad?

GS: Yeah. So we do know that people ate fast food and take out quite a bit more during the COVID-19 pandemic. There are some other kinds of more nuanced results that I can’t quite recall offhand. I’m sure we all can remember ordering DoorDash a time or two during Covid when we, frankly, could have gone and picked up the food, at the very least to save that 20 bucks. But, I mean, that’s now why we have such a thriving delivery industry.

TP: Well, what are some other large questions that you still wonder about with stress and eating that researchers have not really worked out. What are the things that we need to understand to really understand this phenomenon better.

GS: Yeah, I think that I would love to see more work examining particular types of food choices and how those differ as a function of stress. So, moving beyond hyper-palatable. Is it the case that we see specific forms of hyper-palatable food consumption increase without seeing others? And even, can we do away with the term hyper-palatable and really talk about high fat, high sugar or high sodium. Things like that.

It’s been studied to a degree. There are some studies on this, but, less so within the larger economic types of studies. Although there are, again, some studies that have done so, it’s just a little bit messy. The literature on this is quite messy, actually.

TP: Let’s talk about you work in general. Your research is focused on stress. Why? What brought you to this subject?

GS: Yeah, so, a couple reasons. I’m particularly interested in the intersection between stress and cognition. What brought me to that research interest? You can talk about in a few different ways. One of them is it was just the intersection of the expertise that my earliest advisors had. And I saw that there wasn’t as much work on the topic as you would expect. So I kind of started to make that my area of interest. That’s the, kind of pragmatic answer.

The subjective answer, that I feel is more accurate even though I’m not sure how true this is, is that when I was working between undergrad and grad school in a group home, I saw youth when they were stressed out do things that they would really regret doing later on.

And then I began to see some of the same things in me, right? Like, I eat the pint of ice cream from time to time. Although not quite to the same degree, I started to think, well, maybe this failure of self-regulatory behavior under stress is something that is common and yet understudied. And so, I want to study it.

TP: We’ll talk about some of the work that you’ve done so far. I mean, what are specifically some of the experiments you’ve done? And I know, your graduate students also, and your undergraduates also, do experiments, so maybe talk about some of the work you’ve directed with them. What are the questions you’re trying to answer there?

GS: One study that we wrapped up pretty recently was examining how different things that happened to us during stressful experience might influence how we remembered those experiences. So, in this case we actually didn’t stress anyone out. We just had them write about stressful events that had happened that contained specific characteristics. Either they did this or they didn’t do that.

And we wanted to see how it influenced the types of information that people were retrieving about those memories. And we found some interesting results. Another one of my students right now is — he just finished putting together a study examining how stress influences particular form of decision making. And before coming here, I actually just participated in it as a participant.

TP: Is that something you do often?

GS: Well, I do ask my students to always have me be participant zero in their studies. I want to make sure that everything is implemented correctly. And, just that everything kind of comes together as it should before we run other participants through it. I also feel like it’s only fair if I’m asking somebody else to do this, that I’ve done it myself.

But again, we don’t only do stress studies. So, if you sign up for a study in my lab, you might not have any of these things happen to you.

TP: Well, can you talk about what the experience was like of being in a subject just a few minutes ago in one of your students experiments.

GS: It’s stressful. I’m all discombobulated.

TP: I would never know. I would never know. Can you talk about how you stress people. How do you induce stress in these experiments?

GS: So, okay, so we induce stress by a number of different means. They are all means that you could experience in everyday life just kind of walking around or in conversation with someone else. So, one of the most common ways that we induce stress is actually just interviewing people. We ask them to tell us about themselves, and people just don’t like speaking about themselves for a certain period. Some people do and they’re great at it, but most people that that’s not the case.

It’s also we use things that can heat or cool water to certain temperatures that people choose to get into anyways. So one of the stressors that we use, we heat water up to 115 degrees, like you can walk around in that. It’s not going to cause any tissue damage. But it really hurts. And so people don’t like to have their arm submerged in water that warm for a few minutes period. Things like that. They’re minimal or no risk, but, they’re particularly effective at making people feel less than ideal.

TP: Well, you’ve dedicated your research and your professional life to studying stress. Are you better at handling stress in your personal life than before?

GS: I would say so. For a while, I don’t think that I would have, but I have gotten to the point where I’ve learned the particular situations that are likely to elicit stress and how I can deal with those in ways that are maybe a bit more productive than I used to.

TP: Excellent. Well, Grant, thank you so much for the conversation. It’s been really fun.

GS: Yeah. Thank you for having me here.

TP: Short Talks from the Hill is now available wherever you get your podcast. For more information and additional podcasts, visit ArkansasResearch.uark.edu, the home of science and research news at the University of Arkansas. Music for Short Talks from the Hill was written and performed by local musician Ben Harris.