Neurocognitive alterations in obese candidates for bariatric surgery and psychological predictors of successful weight loss

Background: Neurocognitive alterations have been related to severe obesity, especially in terms of reduced cognitive control and enhanced attention toward food-related stimuli. Laparoscopic Sleeve Gastrectomy (LSG) is a bariatric surgery promoting weight-loss via physiological, metabolic and behavioral changes. Initial evidence for cognitive improvement after surgery exist, suggesting a resolution of obesity-induced changes in reward functions and cognitive control. However, neurophysiological correlates of these processes are poorly investigated and longitudinal studies are needed in this direction. Despite the positive outcomes of LSG, some patients fail to reach successful post-surgery excessive weight loss (EWL). Possible psychological predictors of post-surgery outcomes have been suggested, although contrasting findings are present and studies investigating multiple psychological predictors are warranted. Aims: This thesis aims at investigating neurophysiological and behavioral correlates of the alteration in cognitive control and food-related attention in obese candidates for LSG and the possible improvement at 12 months post-surgery. Another aim was to identify multiple psychological predictors of successful weight loss at 12 months post-LSG. Methods: Cognitive control in presence of food-related stimuli was measured using a modified version of the Simon task, during EEG registration. In the first study, 24 obese candidates for LSG were compared with 28 normal-weight individuals, while in the second study patients were followed up at 12 months post-LSG, with the same measures of food-related cognitive control. In the third study, multiple preoperative psychological predictors of successful EWL % at 12 months post-LSG were assessed in 69 patients. Predictive variables included in the model were psychopathological symptoms, dysfunctional eating attitudes, and impulsivity trait. Results: In the first study, food-related images interfered with cognitive control in obese individuals as assessed with RTs; ERPs measures showed a prefrontal N1 component higher for food in both groups, indexing early attentional capture of food images. Longer P2 latency and smaller N2 amplitude were present in obese individuals. In the second study, a reduction of food-related interference was found in both RTs and P3 amplitude toward food. ERPs indices of general attention (P2 amplitude) and cognitive control (N2 amplitude) were enhanced after LSG. In the third study, a logistic regression showed that age and attentional impulsivity trait positively predicted successful EWL while anxiety symptoms negatively predicted successful EWL. Discussion: Attentional bias toward food-stimuli interferes with cognitive control in obese candidates for bariatric surgery. This food-related interference on cognitive control is reduced post-LSG. Neurophysiological indices suggested a reduced cognitive control in obese seeking LSG, which can be enhanced post-surgery. Specifically, enhancement of N2 amplitude in frontal electrodes after surgery may suggest higher recruitment of frontal areas during conflict detection processes post-LSG. In a larger sample of obese seeking LSG, elevated preoperative anxiety symptoms negatively predict successful EWL, possibly suggesting the importance of clinical interventions targeting anxiety in bariatric surgery candidates to possibly avoid post-surgery failures. Moreover, the present results on impulsivity trait suggest that restrictive BS procedure such as LSG may be suitable even in patients with moderate impulsivity traits, possibly helping them to avoid risky eating behaviors such as binge eating.