Analysis of changes in gene expression after weight loss. The hypothesis tested in this study was that the weight loss caused by Roux-en-Y Gastric bypass may alter the expression of genes involved in multiple molecular pathways related to obesity. The results will generate important data for studies involving treatment of obesity, which is characterized as a multifactorial disease that affects thousands of individuals worldwide. Total RNA obtained from peripheral blood mononuclear cells of women with obesity who underwent Roux-en-Y gastric bypass in pre- and postoperative periods (6 months). Women with a normal weight were used as controls.