**1. Introduction**

Several authors postulate that eating disorders (EDs) and obesity form part of a broad spectrum of eating- and weight-related disorders [1]. Concerning weight status, anorexia nervosa of the restrictive type (AN-R) and the binge eating/purging type (AN-BP) are characterized by being underweight (BMI < 18.5 kg/m2), and bulimia nervosa (BN) by normal weight (BMI 18.5–24.9 kg/m2). Within obesity (BMI ≥ 30 kg/m2), researchers differentiate between Class I (BMI 30–34.9 kg/m2), Class II (BMI 35–39.9 kg/m2), and Class III obesity (BMI ≥ 40 kg/m2) [2]. With respect to eating-related behaviors, patients with AN-R mainly engage in severe food restriction, whereas patients with AN-BP also report binge eating and purging behaviors (e.g., vomiting, laxative abuse, etc.) besides food restriction.

**Citation:** Claes, L.; Kiekens, G.; Boekaerts, E.; Depestele, L.; Dierckx, E.; Gijbels, S.; Schoevaerts, K.; Luyckx, K. Are Sensitivity to Punishment, Sensitivity to Reward and Effortful Control Transdiagnostic Mechanisms Underlying the Eating Disorder/ Obesity Spectrum? *Nutrients* **2021**, *13*, 3327. https://doi.org/10.3390/ nu13103327

Academic Editors: Fernando Fernandez-Aranda, Janet Treasure and Empar Lurbe

Received: 29 August 2021 Accepted: 20 September 2021 Published: 23 September 2021

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**Copyright:** © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

Patients with BN and binge eating disorder (BED) are characterized by regular episodes of binge eating with and without compensatory behaviors, respectively [3]. The causes of obesity are diverse, including genetic, environmental, and behavioral aspects of excessive energy intake, partitioning, and expenditure [4]. Obese patients with a comorbid eating disorder (mainly BED, which is reported in 30% of obese patients) report more eating and weight-related pathology, as well as more general and personality psychopathology [1,5,6], compared to obese patients without BED.

The question remains open as to why patients with AN are able to highly restrict their food intake and become emaciated, whereas other patients binge and overconsume with and without purging behaviors [7,8]. Part of the explanation might be found in interindividual differences in reactive (bottom-up) and regulative (top-down) temperament [7,8]. According to dual-process models, ED behaviors result from the interplay of bottom-up processes (e.g., sensitivity to punishment and sensitivity to reward) and top-down processes (e.g., effortful control) [9]. One of the most applied models of reactive temperament that can be used to explain individual variations in food intake is reinforcement sensitivity theory (RST) [7,10,11], which encompasses two primary motivational systems: the behavioral inhibition system (BIS) and the behavioral activation system (BAS). The BIS is sensitive to stimuli that signal conditioned punishment and the omission/termination of reward and is involved in behavioral inhibition [12]. The BIS is related to personality traits, such as the Big Five neuroticism dimension and Cloninger's harm avoidance dimension [13,14]. The BAS is sensitive to stimuli that signal unconditioned reward and relief from punishment and is involved in approach behavior [12]. The BAS is related to personality traits, such as extraversion and novelty seeking [13,14]. Over the years, the RST has included a third system: the fight–flight system [15]. In 2000, Gray and McNaughton [16] presented a revised version of the RST in which the BAS is responsive to (un)conditioned stimuli of reward and the fight–flight–freeze system is responsive to (un)conditioned stimuli of punishment, while the BIS resolves goal conflicts (e.g., approach-avoidance conflicts).

Besides reactive temperament (bottom-up, automatic), regulative (top-down, controlled) temperament or executive control [17] can also play an important role in the regulation of food intake and weight. Self-regulation is often used interchangeably with terms such as effortful control [18] and self-regulation [19]. Effortful control is also related to particular personality traits, such as the Big Five conscientiousness dimension and Cloninger's self-directedness dimension [17]. It is assumed that effortful control can directly influence ED behaviors or moderate the association between reactive temperamental traits and ED psychopathology, in the sense that a high level of effortful control might help individuals control their reactive temperament and decrease their risk of developing ED psychopathology [20].

Up until now, most studies have investigated BISBAS reactivity and effortful control in patients with EDs or obesity with and without BED (often compared to healthy controls) separately; but none of these studies included patients situated over the whole spectrum of ED/Obesity within a single study. In what follows, we present an overview of the literature on the sensitivity of reward/punishment and effortful control in patients with EDs and obesity.
