Abstract
The worldwide obesity epidemic poses an enormous and growing threat to public health. However, the neurobehavioral mechanisms of overeating and obesity are incompletely understood. It has been proposed that addiction-like processes may underlie certain forms of obesity, in particular those associated with binge eating disorder. To investigate the role of addiction-like processes in obesity, we adapted a model of cocaine addiction-like behavior in rats responding for highly palatable food. Here, we tested whether rats responding for highly palatable chocolate Ensure would come to show three criteria of addiction-like behavior, i.e., high motivation, continued seeking despite signaled non-availability and persistence of seeking despite aversive consequences. We also investigated whether exposure to a binge model (a diet consisting of alternating periods of limited food access and access to highly palatable food), promotes the appearance of food addiction-like behavior. Our data show substantial individual differences in control over palatable food seeking and taking, but no distinct subgroup of animals showing addiction-like behavior could be identified. Instead, we observed a wide range extending from low to very high control over palatable food intake. Exposure to the binge model did not affect control over palatable food seeking and taking, however. Animals that showed low control over palatable food intake (i.e., scored high on the three criteria for addiction-like behavior) were less sensitive to devaluation of the food reward and more prone to food-induced reinstatement of extinguished responding, indicating that control over palatable food intake is associated with habitual food intake and vulnerability to relapse. In conclusion, we present an animal model to assess control over food seeking and taking. Since diminished control over food intake is a major factor in the development of obesity, understanding its behavioral and neural underpinnings may facilitate improved management of the obesity epidemic.
Highlights
Obesity is a major threat to public health, because it increases the risk for diabetes, cardiovascular disease and cancer [1,2]
In order to facilitate the development of uncontrolled eating, a subgroup of the animals (n=36) was exposed to a binge-type model consisting of 4 days of 66% of ad libitum chow alternated with 3 days access to ad libitum chow in combination with Oreo Cookies
After testing for the three criteria of loss of control, we measured responding after devaluation and the propensity to reinstate extinguished responding induced by responsecontingent presentation of the food reward-associated cue or the chocolate Ensure reward itself
Summary
Obesity is a major threat to public health, because it increases the risk for diabetes, cardiovascular disease and cancer [1,2]. The comorbidity between eating disorders and substance abuse disorders may be as high as 40% [18] In this respect it has been suggested that (over) eating and drug use rely on similar neural circuitry [19]. In 2004, Deroche-Gamonet et al developed a model for addiction-like behavior in rats, based on loss of control over cocaine intake [37]. It was found that a subgroup of rats (17,2%) scored within the upper tertile for each criterion, which is far more than would be expected by chance (i.e., 3,6%) These addictionlike behavior-expressing animals appeared to be more vulnerable to reinstatement of extinguished drug seeking, a model for relapse to drug abuse after detoxification [38]. Since addiction-like behavior is associated with increased vulnerability to reinstatement of drug seeking [37], we hypothesized that animals with less control over their food intake would be more prone to cue and foodinduced reinstatement of food seeking after extinction
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