Elsevier

Appetite

Volume 55, Issue 3, December 2010, Pages 420-425
Appetite

Research report
Delay discounting moderates the effect of food reinforcement on energy intake among non-obese women

https://doi.org/10.1016/j.appet.2010.07.014Get rights and content

Abstract

Recent theoretical approaches to food intake hypothesize that eating represents a balance between reward-driven motivation to eat versus inhibitory executive function processes, however this hypothesis remains to be tested. The objective of the current study was to test the hypothesis that the motivation to eat, operationalized by the relative reinforcing value (RRV) of food, and inhibitory processes, assessed by delay discounting (DD), interact to influence energy intake in an ad libitum eating task. Female subjects (n = 24) completed a DD of money procedure, RRV task, and an ad libitum eating task in counterbalanced sessions. RRV of food predicted total energy intake, however the effect of the RRV of food on energy intake was moderated by DD. Women higher in DD and RRV of food consumed greater total energy, whereas women higher in RRV of food but lower in DD consumed less total energy. Our findings support the hypothesis that reinforcing value and executive function mediated processes interactively influence food consumption.

Introduction

Behavioral paradigms to study choice include concurrent choices in which the choice involves responding among alternate reinforcers, or choices that vary over time. These paradigms tap into different processes: measuring responding for current choices is a way to assess relative reinforcing value (RRV) of alternatives, whereas choice that varies over time is a way to assess delay discounting (DD), an important component of impulsivity and executive function. Theories of drug addiction posit that the balance between the motivation to consume drugs and self-regulation of discounting of future consequences (Bickel et al., 2007) or more general self-regulatory abilities (Wiers et al., 2007) is critical for drug use and abuse. The same logic has been applied to hedonic-motivated eating (i.e., eating for pleasure) or overeating, with the hypothesis that eating involves a balance between the motivation to eat regulated by food reinforcement and the control of the impulse to eat (Appelhans, 2009, Epstein et al., 2010, van den Bos and de Ridder, 2006).

RRV refers to how hard someone will work to gain access to that reinforcer using progressive ratio schedules of reinforcement (Epstein, Leddy, Temple, & Faith, 2007). Having higher RRV of food is related to greater energy intake in an ad libitum eating task (Epstein et al., 2004a, Epstein et al., 2004b, Epstein et al., 2007b), and obesity is associated with greater RRV for food (Giesen et al., 2010, Saelens and Epstein, 1996, Temple et al., 2008). Further, greater RRV for a palatable food predicts future weight gain in children (Hill, Saxton, Webber, Blundell, & Wardle, 2009) and abdominal obesity in rats (la Fleur et al., 2007).

Delay discounting is a behavioral paradigm that assesses the choice between two rewards that vary in amount and availability, and discounting occurs when a small immediate reward is chosen over a larger delayed reward (Bickel, Madden, & Petry, 1998). A substantial body of research has demonstrated that drug dependent individuals (Bickel and Marsch, 2001, Bickel et al., 1999, Kirby et al., 1999, Madden et al., 1997, Petry, 2001), gamblers (Dixon et al., 2006, Dixon et al., 2003), and obese individuals (Weller, Cook, Avsar, & Cox, 2008) show enhanced discounting of future rewards. In terms of eating, this may mean that obese persons are likely to engage in impulsive behaviors such as overeating energy-dense foods while discounting future problems associated with obesity.

To date, there is limited research on the interactive effects of RRV for food and DD. Recent models have theorized that inhibitory processes such as DD and reward processes such as RRV of food interact to influence food and drug intake (Alonso-Alonso and Pascual-Leone, 2007, Appelhans, 2009, Bickel et al., 2007, van den Bos and de Ridder, 2006). For example, individuals who steeply discount delayed rewards may find it difficult to resist the immediate gratification of preferred palatable energy-dense foods, whereas those who discount delayed rewards less steeply are better able to resist palatable foods (Appelhans, 2009). The aim of the current study was to examine the independent and interactive effects of the RRV of food and DD on food intake.

Section snippets

Participants

Twenty-eight healthy, non-smoking non-obese women (body-mass-index [BMI] < 30 kg/m2) were recruited from flyers and through an existing database maintained in the laboratory. Interested participants were screened by phone to ensure that they met the inclusion criteria of being female, having no experience with the study methods, and moderate to high liking of the study foods (≥4 on a 7-point Likert scale). Exclusionary criteria included taking medications that could influence taste, appetite, or

Preliminary results

Twenty-eight women were enrolled in the study; however, k values could not be calculated for three women who had indifference points that did not fit the hyperbolic discounting function. In addition, one participant was a consistent outlier in regression models testing our hypotheses, and thus was excluded from all analyses. Analysis and descriptives will be presented for the remaining 24 subjects. No significant differences in BMI, age, education, and eating behaviors were observed between the

Discussion

The current study replicated the observation that individuals who respond more for food in the RRV task consume more food in an ad libitum eating task than individuals who respond less (Epstein et al., 2004a, Epstein et al., 2004b, Temple et al., 2008), and that non-overweight participants respond more for non-food alternatives than food (Temple et al., 2008). The effect of the RRV of food was moderated by DD, such that women who showed higher discounting of future rewards and higher RRV of

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      Reinforcer pathology relates the powerful reinforcing effects of food (or drugs) with poor impulse control to understand excess food or drug consumption [59-62]. People who are high in food reinforcement, have a brief temporal window for decision making and discount the future, consume more food in a laboratory environment [63], have more obesity [64], and lose less weight in a behavioral weight control program [65]. Reinforcer pathology theory relates reinforcing value to the temporal window of people's choices.

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    This research was supported by grants from the Variety Club/Kalieda Health Foundation and the National Institute of Drug Abuse R01 HD 39778 awarded to Dr. Epstein, and the National Science Foundation's Alliances for Graduate Education & the Professoriate Program (AGEP) at the Pennsylvania State University and Ruth L. Kirschstein National Research Service Award grant F31 HL092721 awarded to Ms. Rollins. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Heart, Lung, and Blood Institute or the National Institutes of Health. We thank Lora G. Roba and Tinuke Oluyomi for their help with data collection and entry, and Jochebed Gayles, Mary Lai, Jackie Wiersma, and Claudio Ortiz for their assistance in revising the manuscript. Dr. Epstein is a consultant to Kraft foods and NuVal/ONQI.

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