The objective of this study was to analyze the factors associated with change in body mass index (BMI) and with percentage of excess weight loss (%EWL) in patients undergoing Roux-en-Y gastric bypass (RYGB). The following factors were analyzed: sex, age, surgical access (laparotomy vs. laparoscopy), preoperative BMI, waist circumference (WC), type 2 diabetes mellitus (T2DM), high blood pressure, and dyslipidemia.