Karolien van den Akker

From lab to clinic: Extinction of cued cravings to reduce overeating

Food cue reactivity is a strong motivation to eat, even in the absence of hunger. Therefore, food cue reactivity might sabotage healthy eating, induce weight gain and impede weight loss or weight maintenance. Food cue reactivity can be learned via Pavlovian appetitive conditioning: It is easily acquired but the extinction of appetitive responding seems to be more challenging. Several properties of extinction make it fragile: extinction does not erase the original learning and extinction is context-dependent. These properties threaten full extinction and increase the risk of full relapse. Extinction procedures are discussed to reduce or prevent the occurrence of rapid reacquisition, spontaneous recovery, renewal and reinstatement after extinction. A translation to food cue exposure treatment is made and suggestions are provided, such as conducting the exposure in relevant contexts, using occasional reinforcement and targeting expectancy violation instead of habituation. A new hypothesis proposed here is that the adding of inhibition training to strengthen inhibition skills that reduce instrumental responding, might be beneficial to improve food cue exposure effects.

How partial reinforcement of food cues affects the extinction and reacquisition of appetitive responses: a new model for dieting success?

Animals and humans can easily learn to associate an initially neutral cue with food intake through classical conditioning, but extinction of learned appetitive responses can be more difficult. Intermittent or partial reinforcement of food cues causes especially persistent behaviour in animals: after exposure to such learning schedules, the decline in responding that occurs during extinction is slow. After extinction, increases in responding with renewed reinforcement of food cues (reacquisition) might be less rapid after acquisition with partial reinforcement. In humans, it may be that the eating behaviour of some individuals resembles partial reinforcement schedules to a greater extent, possibly affecting dieting success by interacting with extinction and reacquisition. Furthermore, impulsivity has been associated with less successful dieting, and this association might be explained by impulsivity affecting the learning and extinction of appetitive responses. In the present two studies, the effects of different reinforcement schedules and impulsivity on the acquisition, extinction, and reacquisition of appetitive responses were investigated in a conditioning paradigm involving food rewards in healthy humans. Overall, the results indicate both partial reinforcement schedules and, possibly, impulsivity to be associated with worse extinction performance. A new model of dieting success is proposed: learning histories and, perhaps, certain personality traits (impulsivity) can interfere with the extinction and reacquisition of appetitive responses to food cues and they may be causally related to unsuccessful dieting.

Food Cue Reactivity, Obesity, and Impulsivity: Are They Associated?

Heightened reactivity to food-associated cues and impulsive responding to these cues may be important contributors to the obesity epidemic. This article reviews the evidence for a role of food cue reactivity and impulsivity in food intake, body mass index, and weight-loss success. Inconsistencies in defining and measuring these constructs create difficulties in interpreting findings; however, evidence does support their role in obesity. The relationship between food cue reactivity and impulsivity may depend on the measurement used, but some studies have demonstrated that interactions between these constructs rather than direct effects are important in accounting for food intake pattern. Thus, multimodal assessment of both constructs is recommended. Future research would benefit from standardized definitions, measures, procedures, and reporting to enhance comparisons across studies. Implications for therapy are discussed and suggestions for further research are provided.

Violation of eating expectancies does not reduce conditioned desires for chocolate

Although eating desires can be easily learned, their extinction appears more difficult. The present two-session study aimed to investigate the role of eating expectancies in the short and longer-term extinction of eating desires. In addition, the relationship between eating desires and conditioned evaluations was examined to test whether they might share a similar mechanism. It was hypothesized that the short-term extinction of eating desires would be more successful after the disconfirmation of eating expectancies (instructed extinction or IE), while resulting in worse longer-term extinction because omission of the food reward during extinction is not surprising. In contrast to the hypotheses, it was found that IE had no effect on the short-term and longer-term extinction of eating desires. Eating desires correlated with conditioned evaluations only to some extent. It is concluded that eating expectancies do not mediate the short-term extinction of conditioned eating desires. In addition, their longer-term extinction does not appear to be facilitated by a greater violation of eating expectancies. This suggests that it might not be necessary to focus on expectancy violation in cue exposure therapy to reduce eating desires.

Enhancing inhibitory learning to reduce overeating : Design and rationale of a cue exposure therapy trial in overweight and obese women

The prevalence of overweight and obesity has increased substantially over the last decades. Weight loss attempts in overweight individuals are common, though they seldom result in successful long-term weight loss. One very promising treatment is food cue exposure therapy, during which overweight individuals are repeatedly exposed to food-associated cues (e.g., the sight, smell and taste of high-calorie foods, overeating environments) without eating in order to extinguish cue-elicited appetitive responses to food cues. However, only few studies have tested the effectiveness of cue exposure, especially with regards to weight loss. For exposure treatment of anxiety disorders, it has been proposed that inhibitory learning is critical for exposure to be effective. In this RCT, we translated techniques proposed by Craske et al. (2014) to the appetitive domain and developed a novel cue exposure therapy for overeating aimed at maximizing inhibitory learning. The current RCT tested the effectiveness of this 8-session cue exposure intervention relative to a control intervention in 45 overweight adult (aged 18-60) females at post-treatment and 3-month follow-up, of which 39 participants completed the study. Weight loss, eating psychopathology, food cue reactivity, and snacking behaviour were studied as main treatment outcomes, and mediators and moderators of treatment effects were studied. The presented study design represents an innovative effort to provide valuable clinical recommendations for the treatment of overeating and obesity.

Altered appetitive conditioning in overweight and obese women

Overweight and obese individuals show increased psychological and physiological reactivity to food cues and many of them have difficulties in achieving long-term weight loss. The current study tests whether abnormalities in the learning and extinction of appetitive responses to food cues might be responsible for this. Overweight/obese and healthy weight women completed a differential appetitive conditioning task using food as rewards, while eating expectancies, eating desires, conditioned stimulus evaluations, salivation, and electrodermal responses were assessed during an acquisition and extinction phase. Results suggested reduced discriminative conditioning in the overweight/obese group, as reflected by a worse acquisition of differential eating desires and no successful acquisition of differential evaluative responses. Some evidence was also found for impaired contingency learning in overweight and obese individuals. No group differences in conditioned salivation and skin conductance responses were found and no compelling evidence for differences in extinction was found as well. In sum, the current findings indicate that overweight and obesity may be characterized by reduced appetitive conditioning. It is suggested that this could be causally related to overeating via stronger context conditioning or a tendency towards overgeneralization in overweight and obese individuals.

Validation of prospective portion size and latency to eat as measures of reactivity to snack foods.

In experimental studies that investigate reactivity to the sight and smell of highly palatable snack foods, ad libitum food intake is commonly used as a behavioural outcome measure. However, this measure has several drawbacks. The current study investigated two intake-related measures not yet validated for food cue exposure research involving common snack foods: prospective portion size and latency to eat. We aimed to validate these measures by assessing prospective portion size and eating latencies in female undergraduate students who either underwent snack food exposure or a control exposure. Furthermore, we correlated prospective portion size and latency to eat with commonly used measures of food cue reactivity, i.e., self-reported desire to eat, salivation, and ad libitum food intake. Results showed increases in prospective portion size after food cue exposure but not after control exposure. Latency to eat did not differ between the two conditions. Prospective portion size correlated positively with desire to eat and food intake, and negatively with latency to eat. Latency to eat was also negatively correlated with desire to eat and food intake. It is concluded that the current study provides initial evidence for the prospective portion size task as a valid measure of reactivity to snack foods in a Dutch female and mostly healthy weight student population.

Appetitive conditioning to specific times of day

Human laboratory studies have shown that eating desires are easily learned through classical conditioning: after a few pairings of an initially neutral stimulus (e.g., a box) with the intake of palatable food (e.g., chocolate), the stimulus elicits increased eating expectancies and eating desires (acquisition). After repeated non-reinforced presentations of the chocolate-associated stimulus, eating expectancies and desires decrease again (extinction). It is commonly assumed that eating desires in daily life are acquired and extinguished in a similar manner, but to date, this has not been empirically tested. In two studies, we examined whether the repeated consumption of chocolate at a specific time of day elicits increased eating expectancies and eating desires over a period of 5 days (study 1) or 15 days (study 2), and relative to a time of day not paired with chocolate intake. Further, it was tested whether acquired responding diminishes again during extinction (study 1). Ecological momentary assessment was used to carry out the studies in daily life. Results showed that eating expectancies were acquired in both studies. Only in study 2, eating desires were also successfully learned. It is concluded that eating expectancies and eating desires can be conditioned to ecologically valid cues and under real-life circumstances. This highlights the importance of associative learning processes in the experience of eating desires in daily life.

Pre-exposure to high- versus low-caloric foods: Effects on children's subsequent fruit intake

The effects of pre-exposure to high- versus low-caloric foods on fruit intake were investigated. A total of 56 children participated in this study, and were randomly assigned to an exposure condition: high-caloric food, low-caloric food, or control. Children who were pre-exposed to a high-caloric food ate more fruit than did those pre-exposed to a low-caloric food. These findings suggest that pre-exposure to high-caloric foods stimulates subsequent intake, including intake of foods that were not previously exposed, while pre-exposure to low-caloric foods does not appear to arouse appetite.

What works better?: Food cue exposure aiming at the habituation of eating desires or food cue exposure aiming at the violation of overeating expectancies?

OBJECTIVE This study tested the role of habituation of eating desires and violation of overeating expectancies during food cue exposure in obese women. METHOD 52 obese females were randomised into a two-session exposure condition aimed at habituation, a two-session exposure condition aimed at expectancy violation, or a no-treatment control condition. Eating in the absence of hunger of foods included during cue exposure (i.e., exposed foods) and foods not included during cue exposure (i.e., non-exposed foods), and duration of exposure were measured. RESULTS Both cue exposure conditions ate significantly less of the exposed foods compared to the control condition, though there were no differences between both types of exposure. No differences were found between conditions regarding the eating of non-exposed foods. In addition, the duration of exposure was not different between both cue exposure conditions. CONCLUSIONS While food cue exposure in obese women led to less eating of exposed foods, focusing on either habituation of eating desires or expectancy violation did not matter. It is discussed why exposure works.