What works better? Food cue exposure aiming at the habituation of eating desires or food cue exposure aiming at the violation of overeating expectancies?
Introduction
Worldwide, the obesity prevalence has reached dramatic proportions, and the necessity for effective interventions is high (Flegal, Kruszon-Moran, Carroll, Fryar, & Ogden, 2016). The fact that weight loss interventions that aim at a negative energy balance, by reducing energy intake and increasing energy expenditure, have disappointing effects on successful weight loss fuels the search for effective interventions (e.g., Curioni and Lourenco, 2005, Franz et al., 2007). A major cause for weight gain is the eating for hedonic purposes instead of physiological needs, also referred to as eating in the absence of hunger (EAH; Kral et al., 2013, Lowe and Butryn, 2007). EAH can be promoted by several factors, including exposure to food-related cues; these cues can initiate preparatory processes for food intake, including psychological (e.g., eating desires) and physiological responses (e.g., salivary production; Jansen, 1998). Indeed, this so-called cue reactivity has shown to be higher in overweight versus normal weight individuals (Ferriday & Brunstrom, 2011), significantly correlated to food intake in overweight individuals (Jansen et al., 2003), prospectively related to weight gain (Boswell & Kober, 2016), and significantly reduced in successful dieters (who were previously obese) versus unsuccessful dieters (Jansen, Stegerman, Roefs, Nederkoorn, & Havermans, 2010). Hence, it might be important to tackle cue reactivity in interventions in order to achieve successful weight loss.
Cue reactivity might (at least partly) be learned through classical conditioning (Jansen, 1998, Jansen et al., 2016): when specific cues, such as the smell or sight of food, become associated with food intake (unconditioned stimulus; US) through repeated pairings, these become predictors, or conditioned stimuli (CS), of food intake and capable of initiating cue reactivity (conditioned response; CR). Several human laboratory studies found evidence that associations between food intake (US) and initially neutral stimuli (CS) are easily learned, and that – as a result of this learning process - CSs easily acquire the ability to elicit conditioned eating desires (e.g., Bongers et al., 2015, van den Akker et al., 2013). Because many eating desires are so easily acquired through classical conditioning, extinction of such associations might be the appropriate way to decrease the learned cue reactivity. Exactly this is the aim of food cue exposure: to expose participants to CSs, such as the smell and sight of food, while food intake (US) is prevented. Doing this repeatedly enables the development of a new association: the CS does not lead to the US (Bouton and King, 1983, Bouton, 1993, Jansen, 1998). Exposure therapy is theorized to be most effective when inhibitory learning is maximal; the new CS-noUS association should become stronger than the old CS-US association (Craske et al., 2008). Pilot studies have shown that food cue exposure successfully reduces food cravings and binge eating in bulimia nervosa patients (Jansen et al., 1992, Jansen et al., 1989, Martinez-mallen et al., 2007, Toro et al., 2003; see also; Jansen et al., 2016). Further, studies in overweight adult samples have shown that cue exposure is effective in preventing weight regain after successful weight loss (Mount, Neziroglu, & Taylor, 1990), as well as in diminishing EAH of foods that were specifically included in therapy (i.e., exposed foods; Schyns, Roefs, Mulkens, & Jansen, 2016).
Although food cue exposure indeed seems beneficial for overeating (Schyns et al., 2016), there is little research available on its working mechanism: why is it effective? According to the influential Emotional processing Theory, habituation of fear during exposure therapy provides important information as input for changing the pathological fear structure (i.e., emotional processing). Habituation therefore serves as an index of emotional processing during exposure therapy, and should predict treatment outcome (Foa and Kozak, 1986, Foa and McNally, 1996). However, Craske et al. (2008) argue that the degree of habituation during exposure therapy is not consistently related to better treatment outcome. This seems to be true for food cue exposure as well; habituation of cue reactivity was not related to better outcomes (Schyns et al., 2018, Schyns et al., 2016). These findings might have important clinical implications: therapists should no longer focus on diminishing eating desires during exposure sessions. However, this automatically leads to the question what the alternative focus of cue exposure sessions should be.
Craske, Treanor, Conway, Zbozinek, and Vervliet (2014) argue that one should focus on the explicit violation of CS-US expectancies during exposure (Craske et al., 2014). Instead of waiting until fear declines during exposure, therapists should carefully introduce CSs (e.g., high heart-rate) that maximize the mismatch between the expectancy of the US to take place (e.g., heart attack) and the actual outcome (e.g., the absence of the heart attack; noUS), thereby strengthening the CS-noUS association. Using this method, exposure sessions can be stopped when the feared outcome is no longer expected, which might take less time than waiting until fear levels habituate. Exposure sessions for panic disorder with agoraphobia focusing on expectancy violation have shown to result in better treatment outcome compared to exposure sessions focusing on habituation (Salkovskis, Hackmann, Wells, Gelder, & Clark, 2006), and continuing exposure therapy until the expectancy of the feared outcome was 5% or less was superior to exposure therapy that ended at higher expectancies (Deacon et al., 2013). Expectancy violation during exposure seems well-translatable to food cue exposure, as expectancies of overeating and loss of control can be violated (Jansen et al., 2016, van den Akker et al., 2016). Indeed, lower expectancies after food cue exposure have found to be related to less EAH of exposed foods (Schyns et al., 2016).
The aim of the present study is to investigate whether focusing food cue exposure on violation of expectancies is more effective to reduce kcal intake of exposed and non-exposed foods than focusing on habituation of eating desires. Two exposure conditions are compared: one exposure condition focuses two sessions on the habituation of eating desires (Exposure focused on Habituation; ExpHAB), and the other exposure condition focuses two sessions on the violation of overeating expectancies (Exposure focused on Expectancy Violation; ExpEV). Participants are randomly assigned to either the ExpHAB condition, the ExpEV condition, or a no-treatment control condition. It is hypothesized that 1) the ExpEV condition eats less of exposed and non-exposed foods than the ExpHAB condition, while kcal intake in the control condition will be lower compared to both the ExpEV and ExpHAB conditions, and that 2) shorter exposure times are needed for the violation of expectancies (ExpEV) than for the habituation of eating desires (ExpHAB).
Section snippets
Participants
Female obese participants (BMI > 30) who were motivated to lose weight, aged 18–65 years, were recruited through advertisements. The exclusion criteria were: suffering from self-reported smelling problems (indication of anosmia), pregnancy, currently receiving psychotherapeutic or psychopharmacological treatment, and bariatric surgery (pre and post-operative). Participants were randomly assigned to the ExpHAB condition (n = 17), the ExpEV condition (n = 18), or the control condition (n = 17).
Participants
The participants' mean BMI was not significantly different between the ExpHAB condition (M = 34.68, SD = 3.46), the ExpEV condition (M = 34.95, SD = 2.79), and the control condition (M = 36.14, SD = 4.41), F(2,51) = 0.79, p = .460, ηр2 = 0.03. This also held for age, with a mean age of 42.06 years (SD = 8.99) in the ExpHAB condition, 46.67 years (SD = 6.05) in the ExpEV condition, and 45.94 (SD = 8.58) in the control condition, F(2, 51) = 1.68, p = .197, ηр2 = 0.06.
Experimental manipulation of eating desires and expectancy violation during food cue exposure
Average baseline, peak and
Discussion
The aim of the present study was to investigate whether aiming food cue exposure at expectancy violation is more effective than aiming sessions at habituation of eating desires. It was found that both exposure aimed at habituation of eating desires (ExpHAB) and exposure aimed at expectancy violation (ExpEV) led to less intake of exposed foods compared to intake in the control condition. However, the hypothesized difference between the ExpEV and ExpHAB condition was not found. Both exposure
Conflicts of interest
The authors declare no conflict of interest.
Acknowledgements
This work was supported by the Netherlands Organisation for Scientific Research (NWO): Vici Grant 453.10.006, awarded to Anita Jansen.
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2020, Physiology and BehaviorCitation Excerpt :Overeating expectancies were measured before and after exposure, using ‘If, then’ expressions. General expressions like ‘If I have tasty foods in front of me, then I cannot resist to eat it’ and ‘If I eat a small amount of tasty foods, then I cannot stop eating’ were used in three studies [33–35], while Schyns et al. [32] used personalized ‘If, then’ expressions as well. Participants rated how strongly they believed the expressions on 100 mm VASs [32,33,35] or 5-point Likert scales [34], with higher scores reflecting stronger beliefs in the overeating expectancies.
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2020, Journal of Behavior Therapy and Experimental PsychiatryCitation Excerpt :It would also be useful to compare exposure therapy to other treatments such as cognitive therapy, as Cognitive Behavioural Therapy (CBT) is the current standard for eating disorders, including exposure elements in the behavioural part (NICE, 2017). Considerably less kcal consumption of the personal-exposed food after exposure replicates findings of previous cue exposure studies (Schyns et al., 2016; Schyns, Roefs, et al., 2018; Schyns, van den Akker et al., 2018). However, no significant differences were found on kcal consumption of the personal-non-exposed food, or the general-exposed food.
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