Impulsiveness in Reactive Dieters: Evidence From Delay Discounting in Orthodontic Patients

ORIGINAL RESEARCH published: 31 August 2018 doi: 10.3389/fnhum.2018.00347 Impulsiveness in Reactive Dieters: Evidence From Delay Discounting in Orthodontic Patients Wu Zhang 1,2† , Chunmiao Mai 3,4† , Hongmin Chen 5 * and Huijun Zhang 3,4 * 1 The First Affiliated Hospital of Jinan University, Jinan University, Guangzhou, China, 2 School of Stomatology of Jinan University, Jinan University, Guangzhou, China, 3 School of Management, Guangdong University of Technology, Guangzhou, China, 4 Center for Studies of Psychological Application, Guangdong Provincial Key Laboratory of Mental Health and Cognitive Science, School of Psychology, South China Normal University, Guangzhou, China, 5 Mental Quality Education Center, Beijing Technology and Business University, Beijing, China Introduction: Researchers have made efforts to distinguish the behavioral differences and underlying mechanisms that explain the various possible outcomes of dieting (success, failure and relapse). Although extensive research has demonstrated that eating behavior and individual impulsiveness are closely related to subjective appetite and decision making, very few studies have investigated how subjective and appetite impulsiveness is affected by reactive dieting. Methods: In the present study, we utilized the power of food scale (PFS) and the Edited by: Delin Sun, Duke University, United States Reviewed by: Ning Ma, RIKEN Brain Science Institute (BSI), Japan Ying Wang, University of Science and Technology of China, China *Correspondence: Hongmin Chen Huijun Zhang † These authors have contributed equally to this work Received: 28 February 2018 Accepted: 13 August 2018 Published: 31 August 2018 Citation: Zhang W, Mai C, Chen H and Zhang H (2018) Impulsiveness in Reactive Dieters: Evidence From Delay Discounting in Orthodontic Patients. Front. Hum. Neurosci. 12:347. doi: 10.3389/fnhum.2018.00347 intertemporal choice task and to examine subjective appetite and impulsivity of decision making in orthodontic patients. As a result of their orthodontic devices and the subsequent pain and discomfort caused by eating, these patients become reactive dieters. In order to explore the dynamic influence of orthodontic treatment on appetite and impulsiveness, we collected data for both patients and control participants across three testing sections. We also computed a regression model for further exploration in explaining how potential factors contributed to different choices. Results: We found that the orthodontic group scored significantly lower in PFS than the control group, which indicated a suppression in appetite. Besides, reward and waiting time were significant factors in computational perspective. Moreover, although patients showed a bias in choosing smaller, immediate reward options, they exhibited a decrease in the delay discounting rate as treatment progressed. These findings confirm that subjective appetite and impulsiveness were inhibited due to reactive dieting. Keywords: orthodontic patients, reactive dieters, impulsiveness, intertemporal choice, subjective appetite INTRODUCTION People proactively control their diet for a variety of reasons, such as weight control, keeping fit, reducing blood glucose and lipids, religious fasting. During the dieting process, one has to overcome food temptation or even ignore nutritional needs to achieve a healthy balance between subjective desires and objective goals. For dieting to be successful, previous eating habits need to be changed Frontiers in Human Neuroscience | www.frontiersin.org 1 August 2018 | Volume 12 | Article 347 Zhang et al. Impulsiveness in Reactive Dieters eating and appetite do not only involve behavioral inhibition of food stimuli, but are also likely to engage more complex processes of impulsivity inhibition relating to goal-based decision making. However, the aforementioned studies only focused on the participants with obesity or eating disorder, and thereafter have difficulty in distinguishing the effect of dietary habits from the effect of inherent factors, e.g., metabolic capability. In addition, the motivation of proactive dieter who changes his or her eating habits intentionally is associated with inhibiting behavior. Given the scarcity of relevant studies, we aimed to explore more fully the question of whether dietary habits or appetite influence impulsiveness in normal individuals. Orthodontic treatment has a great impact on both the eating habits and appetite of patients especially in the early stage of the procedure. During this stage, arch wire attachments are used to apply direct force to irregular teeth. This inflicts pain and discomfort on patients, which in turn causes dietary restriction. This leads to an alteration in the eating habits of orthodontic patients such that they become more restricted. Thus, the application of orthodontic devices triggers a conflict between the desire to eat food and the oral pain and discomfort that they experience as a consequence of trying to satisfy this desire. In this way it is similar to individuals who proactively overcome food temptation in order to lose weight. That is, orthodontic patients have to overcome eating difficulties and various forms of discomfort caused by orthodontic treatment in the short term in order to achieve future improvement in oral aesthetics and functionality. But they have no specific motivation on diet. Given the notion that orthodontic devices cause patients to modulate their diet in a reactive manner, we can argue that changes in eating habits may affect their ability to balance short-term difficulties with long-term improvements. Through studies of orthodontic patients, it will be possible to develop a deeper understanding about how individual eating habits and appetite influence impulsivity in decision making. Such a conflict between immediate discomfort and future interests lends itself to intertemporal choice (Frederick et al., 2002). This refers to choices in which individuals must make a tradeoff between costs and benefits occurring at different times (Liang and Liu, 2011). The classic example of such a tradeoff involves smaller sooner (SS) rewards and larger longer (LL) rewards. From the perspective of a rational economist, people should choose larger delayed rewards to maximize their interest. However, people are generally biased towards more immediate rewards. This is especially true for individuals who are highly impulsive (Thaler, 1981; O’Donoghue and Rabin, 1999). Mazur (1984) proposed that people tend to discount the subjective value of money as a function of delays in time. He explained this choice pattern mathematically using a hyperbolic function: SV = R/(1 + kT), where SV represents the subjective value of the delayed reward R associated with waiting time T, and k was the delay discounting rate. The first goal of this study was to explore whether appetitive changes brought about by orthodontic devices impact impulsivity in decision (...truncated)