Stress, food relationships and lockdown
So far this episode, we’ve chatted hunger, thirst, and how the microbes in the gut could be involved with our appetite. But hunger isn't the only driver for eating - some of us eat when we're stressed, or feeling a particular emotion. Katie Haylor asked Giles Yeo how these kinds of things work in the brain. But firstly, what science lies behind a food craving?
Giles - I think it feeds into the feeling of hunger. I think it modulates hunger. So let's simplistically split our brain - from a food intake perspective - into two major control centers. Now they're not separate, but conceptually. The first is the fuel sensing area. Okay. And this literally, I guess if we look at it simplistically, it senses how many calories you have used and therefore how many calories you need to eat in order to make up what you've used. Fuel sensor. Okay. And this sits in an area of the brain called the hypothalamus typically. But then there is also another part of the brain and this is called the hedonic region of the brain or the reward area of the brain. Now this is the part of the brain that makes eating feel good. It is also where it controls your cravings and your wants and your needs rather than necessarily how hungry in terms of, from a fuel perspective, you are.
Let's just take an example. We know that when we are really, really, really hungry, the simplest foods in the world taste delicious. A piece of cheese, a little bit of bread, some rice. Hmm, Hmm. But then, the fuller you become, the more picky you become with your food. Okay. So, we know this phenomenon, we go through it every single day. So there, we have an example of when you're really hungry and so therefore you need fuel, your fuel sensor's going "empty, empty, empty", then you're craving levels for certain things either change or the threshold drops because the bread and cheese and simple foods taste absolutely delicious. Whereas the fuller you become, because your fuel sensor's saying "we don't need that much fuel", suddenly what it takes to trigger your cravings, what it takes to trigger your reward pathway is completely different, right? So suddenly bread and rice - ah no. You need a chocolate cake, right? You need something which is highly energy dense to trigger that area of the brain. So those cravings are going to come more from the reward and hedonic areas of the brain, but it influences and speaks to the fuel sensor part of the brain.
Katie - So aside from hunger then, if someone's inclined to eat through stress or particular emotional states, say you're sad or something, is that then tapping into the hedonic pathway that you mentioned, rather than the fuel sensing pathway?
I'm gonna answer this in a sense where we don't actually know with a capital N.... K capital K! I have a PhD, you know... You're absolutely right. There are some people when they're stressed who eat, and some people when stressed don't eat. And this is a different type of stress than tiger stress that is run, run the hell away from, from anything. Everyone universally responds to tiger stress. Otherwise we're going to be dead. Whereas with chronic stress there's a diametrically opposite response to how we actually respond to the stress. And it's the same hormone it's cortisol, right? It's not even different hormones. Exactly the same hormone. And I think where people are going with this is that, stress is unpleasant. And so you want to try and remove that stress. For some people removing that stress is food. Other people maybe need drugs. They may need alcohol. Maybe they do bungee jumping, you know, and maybe they go running, you know, these, these, these crazy people, they go run when they're stressed. So, so, but because it makes them feel better. So I think that's probably where we are.
Katie - It might seem like I'm asking a bit of a flippant question, but I don't think I am actually, when we first started talking, I mentioned I've been visiting the biscuit cupboard more because I'm working from home and I'm socialising virtually from home. I'm basically living in my house, exclusively. What do you sort of forecast as being the consequence of the way that we eat, considering a lot of us have been in our houses for quite a lot of the time over the past six months? How do you feel about our relationship with food collectively, I guess is my question.
Collectively is a strong word. I think that depending on your response to food and how you behave around food, I think the lockdown will have a number of different effects, some positive, some negative. So for me, I found out at the beginning of lockdown, for instance, on a Tuesday, going down before starting the daily routine and make cornbread. Who the hell wakes up at eight in the morning and makes cornbread on a Tuesday? But I love my food! Whereas other people might have gotten stressed during lockdown. And so suddenly there was this chronic stress that was there and you happen to be closer to your fridge, to your kitchen and being able to do what you want. And so therefore those people may have actually ended up, ended up eating more than they would have liked. And obviously then there are people who really love to do their exercise because that was a good outlet for them, but then they didn't actually manage to do that. And so as a result, didn't burn off the calories, which they wish they ate as well. So I think it all depends on who you are.
Now on top of that, I know I was fortunate in lockdown. I was fully paid through lockdown because I had a job. Whereas there were a lot of people who lost their jobs. And so therefore they were then going to have a completely different relationship with food. Because what kind of food was available to them? Did they have to turn towards cheaper foods with longer shelf life? So-called ultra processed foods, for example, which are high in fat, sugar and salt. So I think there's a very complex answer to give into how we would, as a homogenous blob, respond to lockdown and food.
But I think what lockdown would have done, and this is the critical thing...Because our behaviour around food is governed not only by our genes, but by the genes' interaction with the environment, and lockdown was a very, very significant environmental impact, the like of which none of us have seen in our lives, I don't think. This is a very new type of scenario we will be facing. So there will be undoubtedly a huge influence influencing the relationship of many, many, many different people in different ways to food. And let's see what happens, to be fair. I think there will be studies in a few years time looking back upon this time and upon how lockdown has actually influenced average BMI, rates of disease, you know, and everything else. I don't think it's a flippant question at all. I think it's a very, very relevant question. I just can't give you an easy answer.