Performance on the Iowa Gambling Task is related to magnitude of weight loss and salivary cortisol in a diet-induced weight loss intervention in overweight women

Abstract

The overall objective of this study was to examine the relationship between executive function, specifically decision-making, and weight loss. We used the Iowa Gambling Task (IGT) to characterize decision-making and compared performance on this task to weight loss in obese women (n=29) participating in a 12-week controlled, calorie-reduced intervention. We hypothesized that a greater amount of weight loss over the course of the intervention would be associated with better performance on the IGT, assessed at the end of the intervention. The intervention led to significant weight loss of 5.8±3.1kg (p<0.05) and fat loss of 5.1±3.0kg (p<0.05). Body weight and fat mass losses over the 12-week intervention varied widely, ranging from −12.5kg to 0.0kg for body weight and −10.4kg to +0.8kg for fat mass. A greater amount of body weight loss was correlated (r=0.425; p<0.01) with a higher total score on the IGT. Similarly, the reduction in body fat mass was also correlated with the IGT score (r=0.408; p<0.05). We examined other physiological (salivary cortisol), metabolic (resting energy expenditure), and behavioral (food intake; dietary restraint) factors that might be related to differences in the magnitude of weight loss. Of these variables, ad libitum consumption of energy, fat and protein during a buffet meal was inversely related to weight loss (r=−0.428; p<0.05; r=−0.375; p<0.05 and r=−0.472; p=0.01, respectively). The present study is the first to report an association between diet-induced weight loss and performance on the IGT, and this association was specific to the loss of body fat. Our results suggest that differences in weight loss may be linked to executive function that involves decision-making about events that have emotionally or socially salient ramifications. These findings underscore the need to further investigate higher cognitive and neuroendocrine pathways that may influence or be altered by the process of dieting and weight loss.