Study of Effects From Gastric Bypass Weight Loss on Brain Tissue

BACKGROUND: We have identified subtle changes in some brain regions of obese subjects by using a new computerized technique (voxel-based morphometry, VBM) which allows for studying the local structure of the brain by taking very detailed pictures of the brain through magnetic resonance imaging (MRI) and then processing these images with sophisticated statistical software. Some of these regions may interfere with an obese person's ability to predict future consequences of his or her eating behaviors. These changes may explain why people have difficulty losing weight. However, it is not clear whether these changes in the brain are present before or are a consequence of weight gain. OBJECTIVES: The main aim of this study will be to evaluate the effects of a large and intentional weight reduction on the brains of obese individuals for assessing the possible reversal of the changes associated with excess body weight. Additional objectives will be a) to determine the possible behavioral correlates of the changes in brain tissue composition associated with a large and intentional weight reduction and b) to confirm the results of our previous exploratory analysis showing that human obesity is associated with changes in brain structure in areas related to the regulation of eating behavior. DESIGN: This is a longitudinal protocol mainly focused on obese patients undergoing roux-en-Y gastric bypass (RYGBP), which represents the most effective approach currently available to achieving substantial weight loss, thus maximizing our chances of detecting significant changes in brain tissue composition. Therefore, we propose to study brain morphology and the metabolic and behavioral characteristics of 40 obese patients undergoing RYGBP prior to and 3, 6, 12, 24, and 48 months after the surgery. Forty lean subjects (at 0, 12, 24, and 48 months) will also be studied for comparison. OUTCOME MEASURES: The volumes of the different components of the brain by VBM of MRI pictures; metabolic parameters relevant to the relationship between obesity and the brain by measuring fasting concentrations and postprandial responses of some metabolites; the ability to regulate reward and behavior by specific tasks and questionnaires; the ability to detect and discriminate smells by olfaction tests.