Cognitive-motivational determinants of fat food consumption in overweight and obese youngsters: The implicit association between fat food and arousal

Abstract

Cognitive-motivational accounts of fat food intake propose an association between fat food and action dispositions, which are according to the biphasic emotion theory of Lang [(1995). The emotion probe. Studies of motivation and attention. American Psychologist, 50, 372–385; Lang, P.J., Bradley, M.M., & Cuthbert, M.M. (1997). Motivated attention: Affect, activation and action. In P.J. Lang, R.F. Simons & M.T. Balaban (Eds.). Attention and orienting: Sensory and motivational processes (pp. 97–134). Hillsdale, NJ: Lawrence Erlbaum Associates, Inc.] characterized by high levels of arousal. In two experiments, this association was investigated in lean and overweight youngsters. In the first experiment, 29 overweight and 29 lean youngsters conducted two Implicit Association Tasks (IAT; Greenwald, A.G., McGhee, D.E., & Schwartz, J.L. (1998). Measuring individual differences in implicit cognition: The implicit association test. Journal of Personality and Social Psychology, 74, 1464–1480.). In a positive arousal IAT, implicit associations between fat vs. lean food, and high and low arousal words with a positive valence were assessed. In a negative arousal IAT, high and low arousal words with a negative valence were used. A second experiment was conducted to replicate Experiment 1 in 29 youngsters with severe obesity and 29 lean peers. The results revealed strong implicit associations between fat food and arousal in both the overweight and the control group. No differences were found between the groups, nor between the positive and the negative arousal task. These results are related to cognitive-motivational theories of fat food intake.

Introduction

Several studies have demonstrated that overweight and obesity are related to excessive dietary fat (Bray, Paeratakul, & Popkin, 2004; Lissner & Heitmann, 1995; Schrauwen & Westerterp, 2000). For treatment and prevention purposes, research on the underlying dynamics of fat food consumption is pivotal. In recent years it has become clear that excessive eating shares many characteristics with addiction. For instance, similarities have been noted in the domain of cognitive and neural mechanisms (Berridge & Robinson, 2003; Kelley, Schiltz, & Landry, 2005). This observation can be taken to increase the understanding of cognitive-motivational processes underlying excessive eating.

It has been argued that obesity may be related to heightened arousal levels in response to food cues (Rodin, Schank, & Striegel-Moore, 1989). Influential models, derived from addiction research, have been used to explain excessive food intake (Jansen, 1998; Wardle, 1990). In these models it is assumed that through a learning process, sensorial cues predictive of eating (e.g., the sight and the smell of palatable food) come to elicit anticipatory arousal. These responses are experienced as craving and may trigger food intake. Elevated arousal in response to food cues can also be related to the biphasic theory of emotion and attention (Lang, 1995; Lang, Bradley, & Cuthbert, 1997). This theory proposes affective valence and arousal as crucial determinants of two mutually opposed motivational systems, an appetitive (consummatory) and an aversive (defensive) system. The affective valence towards a stimulus determines the direction of a motivational state, whereas the disposition or urge to act depends upon the level of arousal. According to this theory, craving, or a strong desire for food, is determined then by the combination of a positive attitude and a high arousal level (Drobes et al., 2001; Rodríguez, Fernández, Cepeda-Benito, & Vila, 2005).

There is some evidence to suggest that arousal indeed plays a role in obesity. For instance, it has been shown that binge eating, which is often related to obesity (Bruce & Wilfley, 1996; Decaluwé, Braet, & Fairburn, 2003), is related to differential reactivity patterns in skin conductance and blood pressure in response to food exposure compared to normal controls (e.g., Vögele & Florin, 1997). However, other studies failed to replicate this differentiation, with findings indicating that elevated arousal in response to food cues is not unique to individuals with obesity as it is also observed in normal weight controls (e.g., Nederkoorn, Smulders, & Jansen, 2000).

These mixed results on the association between arousal and food in excessive eating may be explained by the application of psychophysiological measures. That is, research in the domain of emotion has shown that there is a relatively low concordance between behavioral, cognitive, and psychophysiological reactions in response to stimuli (Lang (1978), Lang (1979)). This low concordance limits the usefulness of psychophysiological indices to examine arousal associations with food in the context of excessive eating. Although psychophysiological indices have provided some insight in differential arousal patterns towards food cues in excessive eating, they only assess activation of response systems. Alternative measures could provide useful additive information on the cognitive association of food cues with arousal. For instance, using questionnaires, it has been found that exposure to food cues was associated with self-reported arousal feelings (Drobes et al., 2001; Rodríguez, Fernández, Cepeda-Benito, & Vila, 2005). It is important to note that in several of those studies no clear physiological response to food cues was found, despite that food intake was related to self-reported feelings of excitement, restlessness and lack of calmness (Tuomisto et al., 1999; see also Karhunen, Lappalainen, Tammela, Turpeinen, & Uusitupa, 1997).

As generally acknowledged, however, the validity of self-reports can be compromised because of introspective limitations and socially desirable responding (Greenwald et al., 2002; Schwarz, 1999). One way to circumvent these problems is to assess cognitions indirectly, inferring cognitions from behavioral responses rather than self-report. The Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998) is one of the most-known indirect measures. The IAT is a computer-administered reaction time task that examines the relative strength of associations between concepts. Participants have to sort stimuli according to one of four categories, using two response bottoms. There are two target categories (e.g., flowers and insects) and two attribute categories (e.g., positive and negative nouns). The rationale of the task is that the sorting of attributes and targets that share elements of their representation in memory (e.g., flowers and positive nouns or insects and negative nouns), on the same response key will require less time than sorting unrelated concepts, which have few elements in common (e.g., flowers and negative nouns or insects and positive nouns). This pattern of response facilitation is referred to as the ‘IAT-effect’. It has been argued that the IAT is affected less by social desirability and measures other, more automatic, aspects of associations than questionnaires. The task has been used in a wide variety of domains, including obesity research (e.g., Craeynest, Crombez, De Houwer, Deforche, & De Bourdeaudhuij, 2006, 2007; Roefs & Jansen, 2002). Interestingly, until now, IAT studies failed to find different valence associations for high-fat food vs. healthy food in overweight and obesity compared with lean controls (see Roefs & Jansen, 2002; Craeynest, Crombez, Haerens, & De Bourdeaudhuij, 2007). Similar findings have emerged in the field of alcohol addiction. In contrast, however, a modified version of the IAT, in which the association between alcohol cues and arousal was measured, successfully did discriminate between light and heavy drinkers (De Houwer, Crombez, Koster, & De Beul, 2004; Wiers, van Woerden, Smulders, & de Jong, 2002).

The aim of the present study was to investigate the association between fat food and arousal in lean and overweight/obese youngsters. Pictorial stimuli were used as food cues because it has been found that such stimuli are capable of evoking arousal reactions (Drobes et al., 2001; Rodríguez et al., 2005). Two separate arousal IATs were conducted, one with positive and one with negative arousal words. More specifically, in line with the appetitive motivational system as described by Lang (1995; Lang et al., 1997), it was expected that youngsters with overweight and obesity, compared to lean peers, associate fat food more with high arousing positive words than with low arousing positive words. This effect should disappear when arousal is negatively defined. Further, also self-reported valence and arousal towards fat and lean food, and state and trait craving were measured.