Background: The major aim of this study was to investigate whether the motivational salience of food cues (as reflected by their attention-grabbing properties) differs between obese and normal-weight subjects in a manner consistent with altered reward system function in obesity.
Methodology/principal findings: A total of 18 obese and 18 normal-weight, otherwise healthy, adult women between the ages of 18 and 35 participated in an eye-tracking paradigm in combination with a visual probe task. Eye movements and reaction time to food and non-food images were recorded during both fasted and fed conditions in a counterbalanced design. Eating behavior and hunger level were assessed by self-report measures. Obese individuals had higher scores than normal-weight individuals on self-report measures of responsiveness to external food cues and vulnerability to disruptions in control of eating behavior. Both obese and normal-weight individuals demonstrated increased gaze duration for food compared to non-food images in the fasted condition. In the fed condition, however, despite reduced hunger in both groups, obese individuals maintained the increased attention to food images, whereas normal-weight individuals had similar gaze duration for food and non-food images. Additionally, obese individuals had preferential orienting toward food images at the onset of each image. Obese and normal-weight individuals did not differ in reaction time measures in the fasted or fed condition.
Conclusions/significance: Food cue incentive salience is elevated equally in normal-weight and obese individuals during fasting. Obese individuals retain incentive salience for food cues despite feeding and decreased self-report of hunger. Sensitization to food cues in the environment and their dysregulation in obese individuals may play a role in the development and/or maintenance of obesity.