Abstract
Obese individuals have been shown to exhibit abnormal sensitivity to rewards and reward-predicting cues as for example food-associated cues frequently used in advertisements. It has also been shown that food-associated cues can increase goal-directed behavior but it is currently unknown, whether this effect differs between normal-weight, overweight, and obese individuals. Here, we investigate this question by using a Pavlovian-to-instrumental transfer (PIT) task in normal-weight (N = 20), overweight (N = 17), and obese (N = 17) individuals. Furthermore, we applied eye tracking during Pavlovian conditioning to measure the participants’ conditioned response as a proxy of the incentive salience of the predicted reward. Our results show that the goal-directed behavior of overweight individuals was more strongly influenced by food-predicting cues (i.e., stronger PIT effect) than that of normal-weight and obese individuals (p < 0.001). The weight groups were matched for age, gender, education, and parental education. Eye movements during Pavlovian conditioning also differed between weight categories (p < 0.05) and were used to categorize individuals based on their fixation style into “high eye index” versus “low eye index” as well. Our main finding was that the fixation style exhibited a complex interaction with the weight category. Furthermore, we found that normal-weight individuals of the group “high eye index” had higher body mass index within the healthy range than individuals of the group “low eye index” (p < 0.001), but this relationship was not found within in the overweight or obese groups (p > 0.646). Our findings are largely consistent with the incentive sensitization theory predicting that overweight individuals are more susceptible to food-related cues than normal-weight controls. However, this hypersensitivity might be reduced in obese individuals, possibly due to habitual/compulsive overeating or differences in reward valuation.
Highlights
Eye tracking in particular revealed duration orienting biases toward food cues and decreases in pupil diameter [a marker of noradrenergic increases and higher attentional engagement [90, 91]] to high-calorie foods in overweight and obese subjects [92,93,94]. Our results extend these previous reports by showing that goal-directed behavior in overweight individuals is strongly influenced by cues associated with food rewards, as tested by the Pavlovian-to-instrumental transfer (PIT) paradigm, while the influence of neutral cues was similar to the normalweight group
We found that individual differences during Pavlovian conditioning (i.e., “low” versus “high eye index”) interacted with the weight category to influence PIT
We found that PIT effects for food rewards differed as a function of weight status
Summary
The worldwide increase of individuals being overweight or obese produces a high medical and psychosocial burden [1,2,3,4], since this condition is related to several comorbidities, such as cardiovascular disease, which is known as the global leading cause of death [2, 4].One factor which has been hypothesized to influence decisionmaking in the context of ingestive behavior and energy balance [5, 6] is the augmented food marketing [7,8,9,10] creating a so-called “obesogenic” environment, i.e., customers are surrounded by a plethora of food-associated sensory cues reminding them constantly of meals or drinks as for example food packaging images at train stations, Coke commercials on TV, or the two arches of the McDonald’s sign in front of every store.Recent studies in humans have shown that food-associated cues influence behavior even when satiated or when rewards are no longer available [11,12,13,14]. The theory implies that in a first phase, motivational value is directed to the reward itself, and in a second phase, to the cues and objects related to the reward, turning them into attention-grabbing incentives [20] In animals, this process can be measured by the Pavlovian conditioned approach/response, i.e., when animals start to sniff, lick, or bite the lever or food tray, which predicted reward delivery [22,23,24]. This process can be measured by the Pavlovian conditioned approach/response, i.e., when animals start to sniff, lick, or bite the lever or food tray, which predicted reward delivery [22,23,24] Such cues can become motivators and act as reinforcers themselves leading to strong reward-seeking behavior [15, 25, 26]. The PIT phenomenon has been widely investigated in both animals [for review, see Ref. [25]] and humans [11,12,13, 26, 39,40,41,42,43,44,45,46,47,48,49,50,51,52,53,54,55,56,57], making this a useful paradigm for translational research
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