Cognitive Control in Youth Obesity

2017-03-16T04:21:42Z (GMT) by Fernanda Gomes da Mata
Overweight and obesity, the excess accumulation of adipose tissue, have become increasingly prevalent in youth over the past three decades. This rise represents a substantial public health-burden because excess weight in youth confers an increased lifetime risk for a number of diseases including hypertension, diabetes, polycystic ovarian syndrome and various types of cancer. Neuroscience models postulate that the modern lifestyle with its drastic changes in what and how we eat has moved eating behaviour outside exclusively homeostatic motives, bringing to attention the importance of decision-making abilities in making healthy food choices. In the modern food environment, where the appeal and size of food products is maximised, individual differences in decision-making abilities are likely to predict food preferences and outcomes in weight loss treatment.
   This thesis aimed to better understand the neurobehavioural systems that underlie decision-making (i.e., interoception, goal-monitoring and reward-impulsive systems) in overweight and obesity (Aim 1), the impact of weight loss on these systems (Aim 2), and the contribution of decision-making skills to treatment outcome in youth (Aim 3). To achieve Aim 1, I have conducted two Studies: in Study 1, cognitive tasks and functional Magnetic Resonance Imaging (fMRI) were used to cross-sectionally examine to what extent cognitive measures of decision-making under ambiguity and risk are associated with BMI. In Study 2, fMRI was used to cross-sectionally examine whether youth obesity is associated with alterations of insula function (the key brain region for interoception) as indexed by differential correlations between insula activation and perception of interoceptive feedback versus external food cues. To achieve Aim 2, I have conducted Study 3, in which fMRI was used to longitudinally examine if treatment-related weight loss is associated with significant changes in brain activation during risk-based decision-making. To achieve Aim 3, I have Study 4, in which cognitive tasks were used to longitudinally examine whether effort-based decision-making predicts attrition in a weight loss intervention.
   Study 1 examined a sample of 73 young adults (age range: 18-24; BMI range: 18-37) including participants with healthy weight (n=26), overweight (n=26) and obesity (n=21). Participants performed two complementary versions of the Iowa Gambling Task (IGT) and the Risky Choice Task (RCT). The IGT measures decision-making under ambiguity and the RCT measures decision-making under risk. Multiple regression models were applied to examine the association between decision-making and BMI. Study 2 examined a sample of 54 adolescents (age range: 12–18; BMI range: 14-36) with excess weight (n=22) and healthy weight (n=32). Participants performed the Risky-Gains Task (RGT) inside an fMRI scanner, and completed the Heartbeat Perception Task and the Dutch Eating Behaviour Questionnaire outside the scanner. Study 3 examined a sample of 16 adolescents with excess weight (age range: 12-18; BMI range: 22-36). Participants performed the Risky-Gains Task during fMRI both before and after a 12-week weight loss intervention. Study 4 examined a sample of 42 young adults with excess weight (age range: 18-24; BMI range: 25-37). Participants performed the Effort Expenditure for Rewards Task (EEfRT) before undertaking a 12-week weight loss intervention. Logistic regression models were applied to examine to what extent effort-based decision-making predicts attrition in the weight loss intervention.   
   The findings of this thesis provide evidence that youth obesity is associated with less ability to encode the risk associated with disadvantageous decision-making options. This abnormal risk processing is associated with disrupted tuning of the insula system towards bodily feedback. In obesity, the insula system is tuned towards external eating and not towards interoceptive input during risk-based decision-making. This can be due to preexisting characteristics or to obesity related neurocognitive adaptations. The findings of this thesis also revealed that this insula deficit recovers following successful weight and adiposity loss. Furthermore, this thesis links attrition in weight loss intervention to effort-based decision-making. Less willingness to work for uncertain rewards may account for the difficulty experienced by dieters in adhering to treatment.