Abstract
Bariatric surgery is a common treatment option for severe obesity, leading to substantial weight loss and improvements in obesity-related disease. However, there is considerable variability in weight loss outcomes over time. Optimal weight loss is partly dependent on the patient´s ability to initiate and sustain a permanent lifestyle change; hence, the identification of psychological factors implicated in weight loss outcomes is important. An emergent literature suggests that cognitive function, as indicated by performance on neuropsychological tests, both contribute to and are influenced by postoperative weight loss. To date, important issues in this research area remain unclear. Prior prospective surgical studies have mostly investigated direct associations between cognitive function and postoperative weight loss, excluding eating behavior as a factor in this relationship. Further, as most prior prospective studies of postoperative memory function have used data derived from a limited pool of patients, and solely assessed verbal memory, key interpretations regarding the effect of bariatric surgery on memory function remain limited and unchallenged.
The current thesis adds to this growing research field by extending prior findings on these two separate research questions. Specifically, Papers I and II focus on the role of executive function on eating behavior and weight loss, both prior to and following bariatric surgery. Paper III examines changes in postoperative memory function by including measurement modalities not covered in prior studies. All papers use data from the Oslo Bariatric Surgery Study Cognitive, a 2-year prospective observational research project investigating cognitive function in a sample of bariatric surgery patients treated at the Centre for Morbid Obesity and Bariatric Surgery at Oslo University Hospital.
Paper I found that two core aspects of executive function, working memory and inhibitory control, predicted preoperative weight loss and dietary adherence, respectively. Paper II showed that inhibitory control, but not working memory, predicted 1-year postoperative weight loss. In addition, grazing was associated with weight loss, but did not mediate the relationship between inhibitory control and weight loss. Paper III found that verbal and visual memory performance was poorer one year following surgery, with a subsequent return to preoperative performance levels at the 2-year follow-up. This change was not predicted by weight loss or comorbidity.
Overall, findings provide preliminary data that may inspire future investigations of preand postoperative executive function and mediating factors that contribute to weight loss success following bariatric surgery, as well as future studies of the potential consequences of reduced memory after surgery. Further, findings illuminate several factors that signal the need for extended postoperative support to optimize weight loss outcomes.