In the context of the present research, automatic approach and avoidance is relevant to understanding dietary restraint failure, which frequently manifests as disinhibition
(Westenhoefer et al., 1994; Stunkard & Messick, 1985). Impulsivity and impulsive eating behaviour are the common catalysts of disinhibition, and are prevalent in both restrained eaters (Nederkoorn et al., 2004) and in those with bulimic symptoms (Claes et al., 2006). However, implicit food associations and impulsivity, as it might be expected, do not appear to play the same role in AN. Veenstra and de Jong (2011) found that healthy controls had stronger automatic approach tendencies towards high-fat than neutral stimuli, but no difference in their approach towards low fat and neutral stimuli. However, participants with AN did not show this stronger approach towards high fat foods. Furthermore, BMI was negatively correlated with the tendency for automatic approach towards high-fat food in the clinical sample. Explicitly,
participants with AN also reported less craving for high-fat foods compared to controls. These results suggest that people with AN (especially those with lower weights) may not experience automatic approach tendencies towards food, which could contribute to the maintenance of low body weight. These results are consistent with Roefs et al.’s (2005) research in implicit food attitudes in AN, which suggests that people with AN do not have an implicit preference for high- fat, compared to low-fat food. It could therefore be hypothesised that people with AN do not have positive implicit associations with high-fat foods, which inhibits automatic approach tendencies towards these foods, and reduces the probability of disinhibited eating and dietary restraint failure.
In people engaging in dietary restraint (either via elevated restraint, caloric restriction, or dieting – as all three qualify as acts of self control), we might expect a pattern opposite to the one observed in AN: 1) restrained eaters hold positive implicit associations with high-fat foods; 2) dietary restraint results in a state of ego depletion, which 3) increases automatic approach tendencies towards these foods and ultimately 4) results in restraint failure. The
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empirical findings to support this model have been somewhat mixed. Study 2 did not find differences in implicit food attitudes between high-pathology and low-pathology participants, which supports the first aspect of the model: both groups held similarly positive attitudes towards high-fat foods. Veenstra and de Jong (2010) assessed automatic approach tendencies for high-fat and low-fat food in restrained and unrestrained eaters using the manikin version of the Affective Simon Task. Restrained eaters had enhanced approach tendencies towards both high- and low-fat foods, compared to the unrestrained – which is also consistent with the model proposed above. Seibt, Häfner and Deutsch (2007) also assessed approach and avoidance tendencies towards food in a clinical (mixed BN/AN) group and in healthy controls. Both groups were faster to approach than to avoid food stimuli; however, both groups were also faster to approach food if they were hungry (tested before lunch) than if they were satiated (tested after lunch). This suggests that hunger could enhance automatic approach tendencies towards food.
Fishbach and Shah (2006, Study 2) found a somewhat conflicting result pattern using a joystick design in which restrained and unrestrained eaters approached and avoided “food” stimuli or “fitness” stimuli. Restrained eaters were faster to avoid (push) food words than fitness words compared to the unrestrained. However, it must be noted that the study assessed approach and avoidance tendencies towards food relative to another stimulus, rather than contrasting approach and avoidance tendencies for different food types.
2. The present study
Study 3 follows on from the findings of Study 2. Study 2 was designed to assess whether differences in implicit food attitudes or in susceptibility to ego depletion were associated with elevated ED symptomatology. No differences were found in implicit food attitudes between the high-ED and low-ED group – however, participants with elevated ED symptomatology did not have an implicit preference for desserts (high fat) compared to vegetables (low fat). The ego
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depletion procedure did not successfully induce a state of ego depletion, and a further
adaptation of the methodology was unsuccessful. Study 3 was therefore designed to approach the role of implicit food attitudes from a different direction, by assessing implicit food attitudes and automatic approach and avoidance tendencies in elevated dietary restriction/restraint (as both constitute an act of self-control and can therefore be expected to contribute to ego depletion), and specifically in diet failure. However, the hypotheses have remained consistent with the role of ego depletion in restraint hypothesised in Study 2.
2.1. RESEARCH AIMS AND HYPOTHESES
Hypothesis 1. Current dieters will not differ from current non-dieters in their implicit
attitudes towards high-fat and low-fat foods. This is a replication of Study 2 findings
within participants who self-identify as “being on a diet”.
Hypothesis 2. Current dieters will have stronger approach tendencies for high-fat foods
compared to current non-dieters. Current dieters (i.e., people who report “dieting” at
the time of the study) can be expected to be in a state of ego depletion It is hypothesised that positive implicit associations with high-fat food will therefore enhance automatic approach tendencies towards it, as a consequence of this state. This hypothesis also draws on findings by Seibt et al. (2007), which suggest that hunger enhances automatic approach tendencies towards high-fat food.
Hypothesis 3. Unsuccessful dieters will have more positive implicit attitudes towards
high-fat food compared to successful dieters. If diet failure is predicated on the
tendency to engage in impulsive eating behaviour, then stronger positive implicit associations with high-fat food should contribute to a stronger tendency for disinhibition, and therefore unsuccessful restraint, in a state of ego depletion (i.e., following dietary restraint).
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Hypothesis 4. Successful dieters will be more likely to automatically approach low-fat
foods than unsuccessful dieters. As an extension of Hypothesis 3, positive implicit
attitudes towards high-fat food would be expected to manifest as automatic approach and avoidance towards that food type, and vice versa for low-fat food.
3. Method
3.1. PARTICIPANTS
Female participants (N=157) were recruited through a university subject pool. Study advertisements stated an interest in participants who either have, or haven’t, been on a “diet” within the last year (see Terminology section below). Because this yielded unbalanced group recruitment (more non-dieters had responded), the advertisement was subsequently altered to recruit current dieters only. Of the participants recruited, 17 were excluded for failing to meet minimum accuracy criteria on the IAT; 10 were excluded due to equipment malfunction and a further 4 were excluded for failing to follow instructions. The final participant sample therefore consisted of 126 women. Sample size calculations using a mean effect size of d=.48 (based on the following implicit food attitude studies: Seibt, Häfner, & Deutsch, 2007; Veenstra & de Jong, 2010; Veenstra & de Jong, 2011) and a 3 x 2 x 2 (group x stimulus x approach/avoidance) design indicated a minimum sample size of N=80, which is below the actual number of participants recruited. Mean age in the sample was 23.3 (SD=8.0) and mean BMI 21.2 (SD=3.1). The majority of the participants (87%) spoke English as their native language and the remainder were fluent in English (have obtained at least a C in GCSE English, or international equivalent, as per university admissions requirements). Most (51%) were of UK origin, followed by China (21%). Three participants reported an eating disorder diagnosis in the past. Excluding them from
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analyses did not make any significant differences to the results, and they were therefore included in the sample.
Terminology.
In contrast to Study 2, the present study assesses cognitive and behavioural differences of “dieters” and “non dieters”, rather than “restrained” and“unrestrained” eaters. The terminology used throughout this study draws on research by Lowe and Timko (2004b) and Ogden (1993) in identifying current dieters and successful/unsuccessful dieters, respectively. “Dieting” encompasses aspects of both dietary restriction and cognitive restraint – while a restrained eater can be dieting or not dieting, a dieter is, by definition, engaging in behaviour and cognitions which they believe will result in weight loss. In the context of ego depletion, this is arguably a more naturalistic (and therefore ecologically valid) approach, as it allows us to study the outcomes of the “dieting” behaviours in which people naturally engage (whatever these may be). “Dieting” is used throughout the section to refer to cognitive or behavioural changes associated with self-identifying as a “dieter”: i.e., self-imposed changes perceived by the person to contribute to weight loss, including caloric restriction, restriction of the types of food consumed, and/or cognitive restraint. The sections below explain the recruitment and grouping process in more detail.
Current dieters and non-dieters.
In order to address Hypotheses 1 and 2, participants were classified on the basis of their dieting status at the time of data collection. Participants who responded “yes” to the relevant question on the eating habits questionnaire (“Are you currently dieting?”) were classified as current dieters (N=44). Those who responded “no” were classified as current non-dieters (N=82). This classification method reflects the one used by Lowe and Timko (2004b) to identify people who were “dieters” at the time of data collection. Current dieters scored significantly higher, M=2.61 (SD=1.09) on the restraintsubscale of the EDE-Q compared to current non-dieters, M=1.09 (SD=1.09), t(124)=7.43, p=.000, which suggests that the self-reported classification was consistent with self-reported dietary
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behaviour. The current dieters in this study were therefore more likely to be restrained eaters, but cannot be classified as such because group assignment was not done on the basis of the EDE-Q-Restraint subscale.
It must be noted that participant recruitment was specifically targeted towards dieters (i.e., by outlining inclusion requirements for each group) to allow for recruitment of sufficient participants within each group. For this reason the proportion of dieters and non-dieters cannot be considered to be representative of the general population.