Reinforcer pathology's alternative reinforcer hypothesis: A preliminary examination

A psychobioecological model to understand the income-food insecurity-obesity relationship

Food insecurity, defined by unpredictable access to food that may not meet a person's nutritional needs, is associated with higher BMI (kg/m2) and obesity. People with food insecurity often have less access to food, miss meals and go hungry, which can lead to psychological and metabolic changes that favor energy conservation and weight gain. We describe a conceptual model that includes psychological (food reinforcement and delay discounting) and physiological (thermic effect of food and substrate oxidation) factors to understand how resource scarcity associated with food insecurity evolves into the food insecurity-obesity paradox. We present both animal and human translational research to describe how behavioral and metabolic adaptations to resource scarcity based on behavioral ecology theory may occur for people with food insecurity. We conclude with ideas for interventions to prevent or modify the behaviors and underlying physiology that characterize the income-food insecurity-obesity relationship.

Glucose response to sugar challenge moderates the effect of insulin resistance on reinforcing value of sugar-sweetened yogurt

We have shown insulin resistance is associated with the choice of sugar-sweetened over monk fruit sweetened yogurt. This study extends this research by assessing the association between insulin resistance and reinforcing value for sugar versus monk fruit-sweetened yogurt, and testing the hypothesis that this effect is moderated by greater blood glucose response in people with insulin resistance. Eighteen people with overweight/obesity (BMI = 35.8 kg/m2, range 26.2-48.5) with varying degrees of insulin resistance (Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) = 2.6, range of 0.6-8.0) had blood glucose measured for 2 h after a sugar challenge. Over six days, they consumed, in a double-blind fashion, novel flavored-colored sugar or monk fruit-sweetened yogurts, and the reinforcing value of sugar or monk fruit-sweetened yogurts and delay discounting (DD) were measured. HOMA-IR (r = 0.62, p = .006) and insulin (r = 0.51, p = .03) were related to the reinforcing value of sugar-sweetened, but not monk fruit-sweetened yogurt (r = -0.07, -0.10, respectively). The blood glucose area under the curve moderated the relationship between HOMA-IR and the reinforcing value of sugar-sweetened yogurt (p = .02). People with greater HOMA-IR and greater blood glucose excursions responded the most for sugar-sweetened yogurt. These results extend previous research and confirm the hypothesis that individual differences in response to sugar may activate brain reward centers and condition people to prefer high-sugar foods. DD was related to sugar reinforcement (r = -0.46, p = .03), consistent with the idea that those with high sugar reinforcement desire immediate gratification, and DD moderated the relationship between HOMA-IR and the reinforcing value of sugar-sweetened yogurt (p < .001). Research should test whether reducing insulin resistance would permit people with insulin resistance to choose lower-sugar foods.

The Phenotype of Recovery X: Associations between delay discounting, regulatory flexibility, and remission from substance use disorder

INTRODUCTION

Delay discounting (DD) and self-regulation are important predictors of substance use disorder (SUD) outcomes. Further, regulatory flexibility (RF; i.e., selecting, monitoring, and adapting coping techniques based on contextual demands) is related to psychological resilience. However, studies have yet to examine associations among DD, RF, and remission from SUDs among individuals in recovery.

METHODS

Individuals (N = 148) in SUD recovery completed the Context Sensitivity Index (CSI), the Flexible Regulation of Emotional Expression (FREE) Scale, and the Perceived Ability to Cope with Trauma (PACT) Scale to assess RF and, an $1000 hypothetical reward Adjusting Amount Delay Discounting Task. The study considered individuals to be in remission from SUD if they did not endorse any SUD DSM-5 symptom other than craving (except tobacco use disorder) in the past three months. The study team used t-tests to examine differences in RF and DD by remission status. Univariate linear regressions were used to examine the relationship between RF and DD. Finally, mediation models examined the dynamic relationship among DD, RF, and remission status.

RESULTS

Remitted individuals (n = 82) had significantly lower DD (i.e., greater preference for larger, later rewards) rates (p < .001) and higher context sensitivity (p < .001) and coping flexibility (p < .001). The study found significant negative associations between DD and context sensitivity (p = .008), coping flexibility (p = .002), and emotion regulation flexibility (p < .001). Finally, context sensitivity (p = .023) and coping flexibility (p = .009) mediated the relationship between DD and SUD remission.

CONCLUSIONS

Results suggest that individuals in recovery with broader temporal windows can better identify contextual demands and flexibly cope, contributing to improved SUD recovery outcomes.

Delay Discounting and the Income-Food Insecurity-Obesity Paradox in Mothers

Food insecurity, defined as unpredictable access to food that may not meet a person's nutritional needs, is paradoxically associated with higher BMI (kg/m2) and obesity. Research has shown delay discounting, a behavioral economic measure of the preference for immediate rather than delayed rewards, is related to higher BMI, and moderates the relationship between income and food insecurity. Based on this research, we used regression models to test whether delay discounting, consideration of future consequences, and perceived stress were atemporal mediators of the food insecurity-BMI relation in 313 mothers, controlling for demographic variables. A secondary aim was to replicate the finding that delay discounting moderates the relationship between low income and high food insecurity. Results showed that low income was associated with higher food insecurity, and higher food insecurity was associated with higher BMI. Delay discounting was the only variable that was indirectly related to both paths of the food-insecurity-BMI relation. Delay discounting accounted for 22.2% of the variance in the low-income-food insecurity-obesity relation, and the total model accounted for 38.0% of the variance. The relation between low income and food insecurity was moderated by delay discounting. These data suggest that delay discounting is a potential mediator of the relationship between food insecurity and high BMI, which suggests reducing discounting in the future could be a novel target to reduce food insecurity and help people with food insecurity to reduce their excess body weight. Trial Registration. This trial is registered with NCT02873715.

The Effect of Financial Scarcity on Reinforcer Pathology: A Dyadic Developmental Examination

This study investigated the effects of experimentally manipulated scarcity on the reinforcing value of food (RRVfood) and delay discounting (DD), which, together, create reinforcer pathology (RP) among parents and offspring. A stratified sample of 106 families (53 parent/child aged 7−10 dyads & 53 parent/adolescent aged 15−17 dyads) from high- and low-income households visited our laboratory for three appointments. Each appointment included an experimental manipulation of financial gains and losses and DD and RRV tasks. The results showed that, regardless of food insecurity or condition, children had greater RP (β = 1.63, p < 0.001) than adolescents and parents. DD was largely unaffected by acute scarcity in any group, but families with food insecurity had greater DD (β = −0.09, p = 0.002) than food-secure families. Food-insecure parents with children responded to financial losses with an increase in their RRVfood (β = −0.03, p = 0.011), while food-secure parents and food-insecure parents of adolescents did not significantly change their responding based on conditions. This study replicates findings that financial losses increase the RRVfood among adults with food insecurity and extends this literature by suggesting that this is strongest for parents of children.

Psychological Functioning and Health Behaviors Associated with Weight Loss Patterns up to 13.7 Years After Weight Loss Surgery

Weight loss surgery produces dramatic health improvements immediately after surgery, including rapid declines in diabetes. However, less is known about its long-term effects. 124 St. Vincent Bariatric Center patients completed questionnaires on weight and psychological functioning a mean of 7.7 and 13.7 years post-surgery (T1 and T2, respectively). Because mean weight data may mask differing weight trajectories, participants were categorized based on weight over time. Most participants underwent Roux-En-Y gastric bypass (90.3%) and were Caucasian (96%), female (81.5%), and married (69.1%). Mean age at T2 was 64; mean %EWL was 64.9%. Most patients fit into one of three weight change patterns, reaching weight nadir, and regaining by T1 and then, by T2, experiencing (1) Weight Loss (n = 36), (2) Weight Maintenance (n = 37), or (3) Continued Weight Gain (n = 39). Groups differed significantly on body satisfaction, weighing frequency, and conscientiousness, with Weight Gainers significantly lower than other groups on conscientiousness and body satisfaction, and Weight Losers reporting higher frequency of weighing than Maintainers. Bariatric patients can maintain substantial weight loss and positive psychological functioning for many years post-surgery, although weight regain is associated with less body satisfaction. Conscientiousness may signify medical adherence, whereas frequent weighing may be a behavior that promotes ongoing weight loss.

Food reinforcement and habituation to food are processes related to initiation and cessation of eating

An individual bout of eating involves cues to start eating, as well as cues to terminate eating. One process that determines initiation of eating is food reinforcement. Foods with high reinforcing value are also likely to be consumed in greater quantities. Research suggests both cross-sectional and prospective relationships between food reinforcement and obesity, food reinforcement is positively related to energy intake, and energy intake mediates the relationship between food reinforcement and obesity. A process related to cessation of eating is habituation. Habituation is a general behavioral process that describes a reduction in physiological or affective response to a stimulus, or a reduction in the behavioral responding to obtain a stimulus. Repeated exposure to the same food during a meal can result in habituation to that food and a reduction in consumption. Habituation is also cross-sectionally and prospectively related to body weight, as people who habituate slower consume more in a meal and are more overweight. Research from our laboratory has shown that these two processes independently influence eating, as they can account for almost 60% of the variance in ad libitum intake. In addition, habituation phenotypes show reliable relationships with reinforcing value, such that people who habituate faster also find food less reinforcing. Developing a better understanding of cues to start and stop eating is fundamental to understanding how to modify eating behavior. An overview of research on food reinforcement, habituation and food intake for people with a range of weight status and without eating disorders is provided, and ideas about integrating these two processes that are related to initiation and termination of a bout of eating are discussed.