The science behind what's going on in your brain and gut has a lot to do with the impulsive decisions we make around food
Has an intense yearning for a piece of chocolate ever stopped you in your tracks? Do you dream about doughnuts? Fantasise about a big greasy fry? A food craving is an intense desire for a specific food and it can hit due to emotional and psychological reasons. But the science behind what is going on in your gut can have a lot to do with those impulsive decisions.
Dietician Orla Walsh and Dr Sabina Brennan, neuroscientist and Adjunct Assistant Professor at the ADAPT Centre in Trinity College Dublin joined the Today with Claire Byrne show on RTÉ Radio 1 to discuss why we almost go into autopilot when the food we are craving pops into our brains and how to stop. (This piece includes excerpts from the conversation which have been edited for length and clarity - you can hear the discussion in full above).
Why is the food that we crave often high in fat or high in sugar?
"We're craving hyper-palatable food, so in other words really tasty food," says Walsh. "These foods taste really nice, they're easy to eat, and easy to overeat, and these are the foods that we are reaching for especially if the craving is coming from an emotional response."
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"The thing is with these hyper-palatable foods, they kick off a dopamine spike," adds Brennan. "So when you eat you will get a dopamine release triggering pleasurable feelings and motivation to engage in that activity again. That happens when we eat, when we have sex, things that are important for survival. But with these highly processed foods the spike is much, much higher. So get a greater kick out of those."
"It's related to habitual behaviours as well. If you repeatedly engage in something, there's a trigger. It could be your Netflix show that you want to watch, or it could be the time of day, it could be lunch. You engage in the behaviour -- eating the chocolate -- and you get this pleasurable reward. But with time, what happens then is you actually start to anticipate the reward and that's where craving comes in, craving drives it."
Why do we have the cravings in the first place?
There's lots of reasons why we crave foods, says Walsh. "For most people what I describe it as, is picture a lake and we're going to throw a stone into the lake and watch the ripple effect and see what happens downstream. So for example, if someone comes in with extremely high cravings in the evening time, what we might do is look at breakfast. We know that once people eat enough calories at breakfast or enough protein at breakfast and sometimes switch to a savoury breakfast, that can have a big impact on evening eating patterns."
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"Of course, there's habit there. So you quickly get into the habit of having treat-like foods in the evening time and in the same way it doesn't take long to break that habit. But for most people, what I do is I actually look at what's happening at the start of the day," Walsh explains. "Because if we don't eat enough, chasing hunger for the rest of the day. In the same way that if someone starts with a savoury breakfast, they're not getting that sweet craving first thing in the morning. So if you have something sweet for breakfast, you might chase something sweet then for the rest of the day."
Do healthier habits make cravings go away?
Brennan adds that healthier habits can help us manage cravings, but they won't make them go away completely. "Food intake is controlled by two complementary pathways; a homeostatic one and a non-homeostatic one - the hedonistic one, the one that we're talking about here, the craving," she explains.
"But the homeostatic one is the one that should tell us when to eat, when we have low energy. The non-homeostatic, the hedonistic one, that increases our motivation to eat even if we've got no energy depletion. Taking in sugar disrupts the bodies natural ability to sense hunger and satisfaction, so it all gets kind of messed up and your hunger hormones go out of whack."
A lack of sleep, chronic stress and a lack of exercise all make cravings more difficult to address, says Brennan. "So even if you override with a healthy habit -- you can actually come to crave things like apples and healthy food, you can -- it just doesn't have the same sort of spike that the sweet stuff does." Brennan says if you want to start to overcome cravings, what's really important is to take into account the other facts that influence cravings; poor sleep. "If you have disrupted sleep you're inclined to consume about 300 more calories the next day and you'll crave those from fat and from sugar."
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Poor sleep also disrupts the two hunger hormones ghrelin and leptin, which tell you when you're hungry and when you've had enough. "Basically, they get switched around, and you have this thing that says you're more hungry than you actually are," says Brennan. "Same with stress: when cortisol is released it seems to also influence the dopamine and actually encourage you to crave more food. Exercise is a great way around it, because it seems to counteract that, in terms of the craving. It helps immensely."
Your microbiota -- gut bacteria -- play a huge rule in cravings as well, adds Brennan. "It's involved in your second brain and sends messages to your brain. If you have bad gut bacteria, or rather the unhealthy gut bacteria that craves chocolate, it's going to send messages to your brain. So looking after what you eat and eating things like fermented foods -- kaffir, miso -- those kind of things can help actually boost the good gut bacteria and help you overcome those cravings."
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The most important thing is to diversify your gut bacteria, says Walsh. "What we focus on is trying to diversify the gut microbiome. It's not just bacteria, although it's predominantly bacteria, it's also things like yeast and viruses. That's not necessarily a bad thing. I think we've come to terms with the fact that you can have good bacteria and bad bacteria. But the most important thing is to diversify it."
"If we're eating the same thing day in, day out, our gut is eating the same thing day in, day out. So it's really important to focus on variety in your diet. If someone wanted to target [their gut bacteria], we tend to encourage people to have 30 different plants a week. It's not just carbohydrates and fruits and veg, it's herbs and spices, it's nuts, seeds, legumes. It's trying to diversify your plant intake so that you diversify your gut bacteria. That's important because the gut and the brain are constantly communicating. What the bacteria do, is they talk to our nerves and they talk to her brain and vice versa," says Walsh.
