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.
