Cueing for food

When was the last time you were overcome with a desire to eat a particular food? Did you say lunchtime, dinnertime, when I was last hungry and so on? Thank you for playing - next contestant, please. We may want to eat at these times, but it’s rare for such occasions to prompt a desire for something specific. On the other hand, walking past a bakery or pizzeria or curry restaurant can easily produce a desire to consume the source of the aromas we pick up. You’ll perhaps notice that I didn’t include vegetable market or health food shop among these examples, and there’s a good reason for that.

Food sensory cues - sights, sounds (sizzling, for example), smells - are signaling not just the presence of food, but also the food’s palatability. And they are everywhere. The multimedia environment in which we are all immersed in affluent societies means that cues signaling food palatability are present for pretty much the majority of the time we are awake, through television, advertising, and our urban ‘smellscape’.

This is not to say that ‘internal’ cues such as hunger are irrelevant to motivating us to eat. Indeed, hunger makes us much more vulnerable to ‘external’ food sensory cues which mainly come about through learning. That is, our bodies associate the ingested fats and sugars of foods with their flavours and aromas, which not only becomes highly liked as a consequence but also become a powerful trigger for the desire to consume, or wanting. This desire or drive is at least as much about hedonic hunger as it is about an empty stomach (see: Learning to Want for further detail).

It is important not to underestimate the role that cue-elicited wanting plays in overeating. Obesity is much less common in societies where regular mealtimes are observed and snacking is low. It is ‘non-essential’ eating, driven by a desire for food pleasure (read: fat, sugar, salt) that provides the greatest challenge to a health weight. We are all influenced to greater or lesser degrees by external food cues, and we will all tend to eat more of a palatable food than one that is not palatable. But the fact that cues can have such a powerful impact on eating has raised the question of whether those who have difficulty controlling their food intake are somehow more aware or more reactive or perhaps more vulnerable to external cues.

Even if you find chocolate or desserts highly appealing, you may or may not give in to the temptation to indulge when either is available. The idea of eating restraint - habitual monitoring and control of food intake – seems to be important here. Food cues (the sight or smells of a pizza, or even thoughts about food) exert their greatest influence on desire to eat if you are a restrained eater – this isn’t very surprising if you consider that restraint means denying yourself food pleasures.

It is easy enough to think of restrained eaters as wildeyed and salivating, forever battling with urges to eat. But of course restrained eaters as a group must include both those who are successful at resisting these urges – successful dieters – as well as those who succumb. Moreover, even if you are not a restrained eater, you may still be someone who tends to give in to the temptations posed by the sight or smell of your favourite foods. Thus, another characteristic – disinhibition – has been implicated in determining responses to food cues. Many of us have tried to lose weight at some stage. This will often involve a considerable effort to inhibit your desire to consume the palatable foods that you will encounter. If you are effective at doing this, then you can be said to be low in disinhibition (the failure of inhibition); conversely, if resistance is futile, then you can be seen as high in disinhibition.

Irrespective of its origin, when measured on the Three Factor Eating Questionnaire (the other factors are restraint and hunger) (1), up to 50 per cent of women in the USA show high disinhibition, and this percentage is highest in young women. Estimated rates in men tend to be much lower, perhaps around 25 per cent, depending on age and other demographic factors.

Disinhibition is not just about reacting to all foods at all times. Those who show high levels of disinhibition are especially responsive to cues that signal the calorie content of foods and thus prone to ‘wanting’ highly palatable foods: sweet foods and beverages and food high in fat, such as butter, cream and ice cream. And because of the nature of the trait, they tend to act on these desires when palatable food is available and consume more. Those high in disinhibition are therefore not simply gluttons who want to continue to eat, but individuals whose responses to sensory cues are exaggerated.

Needless to say, degree of disinhibition is thought to be crucial in determining successful dieting. It is highest among those dieters who have most trouble maintaining their ideal weight and in dieters who are most bothered by food images that lead to craving. It is, for example, associated with increased chocolate intake by those who identify themselves as ‘chocolate addicts’.

To be able to understand the impact of food cues on eating, disinhibition and restraint need to be considered together. If you are low in disinhibition, it is more likely that you will be a successful restrained eater. If you are not trying to restrain your eating, then your level of disinhibition might seem to be of less concern. But if you do not restrain your eating and you are high in disinhibition, then you will still be highly responsive to palatable food cues. 

How these interactions might influence reactions to palatable foods is illustrated by a study (1) in which a group of women were offered their most tempting snack food – including chocolate, crisps, candy, nuts and cookies. The women were firstly asked to taste a small amount of the snack, and then were given the remainder to take home and asked to come back a day later. Half of the women were instructed not to consume any of the snack until they returned the next day (the temptation condition), while the other half of the group were given no instructions (the control group). On returning to the laboratory the next day, all women were offered their snack to eat and the amount they consumed was measured. Regardless of the group they were in, those who measured low in restraint or those high in restraint but low in disinhibition ate approximately the same amount as they had on the previous day. By contrast, those high in both disinhibition and restraint ate significantly more if they were in the temptation group.

The combination of restraint and a strong tendency to disinhibition therefore made these women particularly vulnerable to the temptation of a palatable food that had been restricted. This is, of course, exactly the set of circumstances that those who experience cravings report during periods of dieting. It is not completely clear as yet whether eating restraint is a risk for weight gain if you are disinhibited or disinhibition is a risk if you diet a lot. Increasingly, though, studies are teasing apart the relative contribution of these factors.

Most recently, Martin Yeomans at the University of Sussex (2) has been characterizing those high in food disinhibition, finding that their responses to food may be in fact a reflection of a more general, underlying personality dimension. He pre-exposed participants varying in both restraint and disinhibition to pictures of ‘unhealthy’ foods and measured their responses on a number of tests of general impulsivity (included a test of willingness to delay reward: $2 now or $10 next month?) and risk-taking. Although none of the tests were specifically related to food or eating, after exposure to food cues, high disinhibition women were more impulsive and higher in risk-taking. In contrast, those high in restrained eating showed no such effects, irrespective of exposure to prior visual cues.

Thus, the trend that is emerging is that disinhibition is the important personality factor that predisposes to weight gain, and this is due to how disinhibition alters your response to food cues. Consistent with this, disinhibited eaters consume far more of an available snack following a high carbohydrate meal than do those low in disinhibition. Moreover, this overeating was not driven by hunger but rather by the hedonic properties of the snack. While it might seem that asking such individuals to restrain themselves is a sensible approach, it is clearly asking for trouble, with the risk of failure being high.

 ____________________________________________

1. Stunkard AJ, Messick S (1985) The three-factor eating questionnaire to measure dietary restraint, disinhibition and hunger. Journal of Psychosomatic Research 29: 71–83.

2. Soetens, B., Braet, C., Van Vlierberghe, L., & Roets, A. (2008). Resisting temptation: Effects of exposure to a forbidden food on eating behaviour. Appetite, 51, 202-205.

3. Yeomans, M. R., & Brace, A. (2015). Cued to Act on Impulse: More Impulsive Choice and Risky Decision Making by Women Susceptible to Overeating after Exposure to Food Stimuli. Plos One, 10, e0137626.

4. Chambers, L. & Yeomans, M.R. (2011) Individual Differences in Satiety Response to Carbohydrate and Fat. Predictions from the Three Factor Eating Questionnaire (tfeq)’, Appetite, 41, 316–23.