Lab #36: The Psychology of Eating

In this article we’ll look at aspects of how our mental processes play a role in how we eat, and look at ways you can use this awareness to eat more in tune with your body.

Fewer things take up more column inches in the lifestyle sections on newsstands than healthy eating and dieting.

Much of the coverage is about macronutrients — which ones we should be eating and which to avoid. Currently the bogey man seems to be carbohydrate and the superhero, protein. As a psychologist I don’t have the expertise to evaluate the nutritional arguments, but as a human I’m pretty confused.

What I do know is that whilst what we consume clearly influences our health, how and why we consume those foods is powerfully influenced by psychological processes, many out of our awareness.

Psychological factors have an important part to play in the global challenge of feeding the world’s population, in terms of influencing what we eat and are willing to try (fried locusts anyone?), and the amount we consume.

In this article we’ll look at aspects of how our mental processes play a role in how we eat, and look at ways you can use this awareness to eat more in tune with your body.

The Human Appetite System

Along with the development of a huge brain, upright gait, opposable thumbs and whatever else makes us such an amazing species, our gut-brain axis evolved to help us navigate the world to meet our nutrient and energy requirements.

This system is truly awe-inspiring.

Three phases of digestion prepare the body for the arrival of food and optimise breakdown and absorption of nutrients:

— The Cephalic Phase occurs before food enters the stomach (starting in fact before it enters the mouth)

— The Gastric Phase is a period in which swallowed food activates activity in the stomach

— The Intestinal Phase begins in the duodenum as a response to the arriving food and it moderates gastric activity via hormones and nervous reflexes

Messages conveying information from each of these phases pass between the brain and the gut, helping regulate our intake. Subjectively, we experience these as hunger and fullness, and degrees of pleasure.

As infants, our appetite was largely regulated by these automatic brain-gut messages. As our perceptual, cognitive and affective processes developed, so did the factors that influenced our food choices, and how we ate.

I can’t do justice here to the complexity of the psychology of eating, but I can outline some of the functions the mind plays in how we eat.

Psychological influences on our eating

Perception

Eating is above all, a sensory experience. Our perception of what we’re eating and what’s happening inside us, plays a powerful role in the amount we eat, and the degree of satiety we experience.

• Interoceptive awareness

Neuronal signals from mechanoreceptors in the stomach wall signal the level of distension produced by the volume of food we are eating. This creates one type of fullness signal, and one that changes with successive mouthfuls.

Slower hormonal feedback which begins in the stomach continues into the duodenum and beyond, producing a second slower wave of feelings of fullness, as qualitative information about what has been ingested arrives in the brain*.

Hunger and fullness signals are, as we will see in this article, subject to influences to do with incoming information from our other senses and subject to cognitive factors.

• Sensory habituation — Taste specific satiety

Barbara Rolls, one of the world’s leading researchers into eating and appetite tells the story of an Italian feast she attended where 14 (yes fourteen) pasta courses preceded dessert. “Each was exquisitely prepared, aromatic, mouth-watering. Yet by the middle of the meal all but the heartiest eaters had given up”. Professor Rolls and her fellow diners abandoned the table and instead chatted and drank, ignoring the last 6 or 7 pasta dishes.

But when dessert arrived, suddenly everyone was interested. They sat down and tucked in. Professor Rolls tells this story to illustrate “taste-specific satiety” — the way we find successive mouthfuls of the same food, or the same sort of food, less pleasant.

It’s one of the mechanisms which helps us stop eating, and it generalises to similar foods. Sweet foods affect how enticing other sweet foods seem, and salty foods affect the appeal of other salty foods. It’s thought that taste-specific satiety evolved to ensure that we eat a balanced diet and consume all the nutrients we need.

In the lab, Rolls found that when people had sandwiches with 4 different fillings, they ate a third more than when they had just their favourite filling in all of the sandwiches.

• Perception of what’s on our plates

Charles Spence’s work (Spence and Piqueras-Fiszman, 2014) on the multisensory nature of taste perception has shown that a range of sensory factors influence our enjoyment of a meal.

Food is judged to be of higher quality when eaten using heavy cutlery. Crockery makes a difference too: a study by Piqueres-Fiszman et al (2011) used three bowls filled with same amount of yoghurt. The bowls only differed in weight. When people held the bowl in their hand whilst eating the yoghurt, the yoghurt in the heaviest bowl was rated as having more intense flavour, more expensive and more liked than that from the lightest bowl.

Desserts taste sweeter on a white plate. Strawberry desserts were rated as 10% sweeter and 15% more flavourful when eaten from white plate compared with black plate.

• Attentional focus

The extent to which we concentrate on what we are eating makes a huge difference to how much we taste our food and to how much intensity and pleasure we get from each bite. People rate sweet, sour and salty drinks as less intense when they are engaged in a demanding secondary task than when they are concentrating on the food (van der Wal and van Dillen 2013).

Goncalves et al studied subjects eating in laboratory conditions, to compare how much they consumed with or without distractions. Each of the participants had sessions on different days, where they came in to the lab and ate until they were satisfied. One day they ate with no distraction, on another they had to use their smartphone whilst they ate and on another they had to read printed articles on subjects that interested them.

Compared with no distraction, using a smartphone or reading increased the calorie intake of what they ate by 15%. There was no difference between smartphone use and reading, so it’s not just distracting tech that has this effect.

Memory

Studying the role of memory in influencing our everyday eating decisions has produced some useful findings.

• Episodic memory of recent eating episodes

Each decision you make about food is, as Higgs and Spetter say in their 2018 paper on the cognitive control of eating, the result of your brain rapidly mapping out many possible outcomes and their expected value. The decision about whether to go for seconds is based on your working memory computing the overall “value” to you of that action, taking into account the expected taste of the food, the future impact of eating the food on your health and the social consequences of eating at that moment. All of these considerations interact with your current metabolic state.

One of these cognitive inputs is our recent memory of eating. Higgs studied what happened in the lab when people were provided with a fixed lunch and then 2–3 hours later asked to recall what they remembered about eating this meal. Recalling today’s lunch led to reduced snacking in the afternoon, but snacking wasn’t reduced when people were asked to recall what they ate for lunch yesterday, or a recent exercising episode. This effect of reduced snacking is larger when recall takes place a few hours after lunch than when it is only an hour after lunch.

They concluded that recall of recent eating inhibits consumption and that episodic memory for recent eating itself plays a part in registering fullness.

• Working memory and relation to cravings

Working memory has an important role in maintaining cravings. Kavanagh et al proposed an “Elaborated Intrusion” theory to reflect two stages of food craving activation.

In the evocatively titled “Imaginary relish and exquisite torture”, Kavanagh describes an initial automatic triggering thought (unconscious intrusion) and the subsequent conscious processing (the elaboration).

The initial trigger — he uses the example of someone mentioning drinking a cup of excellent coffee on a sidewalk café — isn’t under conscious control, but once it arrives in awareness it activates a complex of associations, thoughts, feelings and anticipations and our conscious mind goes to work organising all of these reactions.

Kavanagh talks about how this dual-process (automatic triggering of intrusive thoughts followed by conscious elaboration) may explain cravings. As our thinking about the coffee becomes increasingly elaborated and we remember the last time we enjoyed a fabulous coffee and imagine how nice the next one will taste, we construct an almost life-like image of it.

What may happen now is that you start to become aware of the fact that you are not drinking the fabulous coffee right now — in fact you feel you’re in a state of deprivation when your brain computes the pleasure it could get if it could score a cup right now against how it feels not to have it.

Now, in your “deprived” state, what you’re most aware of is the not-having of the coffee. And your mind turns to how to get one.

With its very limited capacity, your Working Memory may now be full of craving-related material. The good news is that Kavanagh’s group has followed this with the development of Functional Imagery Training. FIT combines the style of Motivational Interviewing with rich multi-sensory goal-related imagery to enhance our ability to switch working memory to a non-food, valued future goal which can effectively disrupt the craving sequence (Solbrig et al 2018).

Enhancing your own enjoyment of eating

With the mismatch between our biological systems governing appetite regulation and our modern food environment, eating has become a minefield for many of us.

Using some of the findings I’ve outlined here, there are things you can do to eat more in tune with your health and wellbeing, and enjoy your food more than ever.

1. Eat from heavy plates

Use your heaviest cutlery, crockery and glassware to enhance the pleasure and satisfaction of your meals.

2. Focus on every bite and savour it

Eat mindfully, savouring your food with full awareness, to perceive all the pleasure that is available in what you’re eating and lay down a good memory of this eating episode.

3. Develop a multi-sensory goal image to do with how you want your eating to be

If you eat foods you crave when you’d prefer to resist, close your eyes and create a rich, multisensory image of a specific situation a few months from now, where you’ll really feel the benefits of no longer giving in to cravings.

It could be a special occasion, or something that’s part of your regular routine like being out for a drink with friends. Spend a few minutes really dropping in to this future scene, using all your senses. Once you’ve created this goal image, give it a name (“Marnie’s wedding”, “Friday drinks” or whatever). When you catch yourself starting to crave something you’d prefer not to eat right now, bring that image to mind in all its richness and notice what happens to the craving, and get on with your day.

Conclusion

Here, I’ve outlined just a few of the psychological aspects of eating — your beliefs about yourself and your self-perception add their own twist to the meal.

And when you sit down with others there’s a whole panoply of social forces that come into play.

Complex and fascinating, the psychology of how we eat is one piece of the jigsaw of the enormous health challenge of our times: how to help people reduce the risks to their health from over-consuming the food that surrounds us.