Date Published: June 29, 2017
Publisher: Public Library of Science
Author(s): Catherine C. Steele, Jesseca R. A. Pirkle, Kimberly Kirkpatrick, Keiko Abe.
Impulsive choice is a common charactertistic among individuals with gambling problems, obesity, and substance abuse issues. Impulsive choice has been classified as a trans-disease process, and understanding the etiology of trait impulsivity could help to understand how diseases and disorders related to impulsive choice are manifested. The Western diet is a possible catalyst of impulsive choice as individuals who are obese and who eat diets high in fat and sugar are typically more impulsive. However, such correlational evidence is unable to discern the direction and causal nature of the relationship. The present study sought to determine how diet may directly contribute to impulsive choice. After 8 weeks of dietary exposure (high-fat, high-sugar, chow), the rats were tested on an impulsive choice task, which presented choices between a smaller-sooner reward (SS) and a larger-later reward (LL). Then, the rats were transferred to a chow diet and retested on the impulsive choice task. The high-sugar and high-fat groups made significantly more impulsive choices than the chow group. Both groups became more self-controlled when they were off the diet, but there were some residual effects of the diet on choice behavior. These results suggest that diet, specifically one high in processed fat or sugar, induces impulsive choice. This diet-induced impulsivity could be a precursor to other disorders that are characterized by impulsivity, such as diet-induced obesity, and could offer potential understanding of the trans-disease nature of impulsive choice.
Impulsive choice is a trans-disease process  that is a common characteristic of individuals who suffer from substance abuse [2–4], obesity [5–8], and gambling issues [3, 9–12]. Impulsive choice behavior is the propensity to choose a smaller-sooner (SS) reward even if choosing the larger-later (LL) reward is the more optimal choice, and it is thought that this pattern of behavior is a potential precursor to disease . Impulsive choice is proposed to emerge from high delay discounting rates, with delay discounting referring to the loss of subjective reward value as a function of delay . Over the past decade, there has been emerging evidence that people who are obese make more impulsive choices [5–8]. While it is clear that there is a relationship between obesity and impulsive choice, the direction and nature of the relationship is not clear. It is possible that 1) trait impulsive choice causes obesity, 2) obesity causes trait impulsive choice, or 3) some third factor, such as diet, causes both.
With many Americans consuming Western diets high in processed fat and sugar, the current study sought to understand how diet affects impulsive choice behavior to potentially elucidate the relationship between obesity and impulsive choice that has been found in humans [5–8]. This is critical as self-control is an important variable in many health behaviors including diet and exercise  and impulsive choice has been implicated as a trans-disease process . In addition, we were able to parse out the effects of diet on bias versus sensitivity to delay (delay discounting rates) to provide an insight into potential mechanisms of diet effects on choice.