Among factors influencing the outcome of bariatric surgery may be genetics and familial risk. The purpose of this study was to assess the etiology of obesity and its impact on hunger, satiety, and food likes in obese patients undergoing Roux-en-Y gastric bypass (RYGB). This study was based on 76 patients undergoing RYGB procedures performed by a single surgeon. A previously described 100-point obesity risk index (ORI) was used to assess familial obesity risk. Hunger and satiety were assessed using a standardized Visual Analog Scale "Snickers" test, and food preferences for regular vs. low-fat potato chips were measured preoperatively and postoperatively. Patients were stratified preoperatively into high ORI (n = 34) and low ORI (n = 42) groups. Before operation, high-ORI patients preferred high-fat (regular) potato chips to low-fat (baked) potato chips, whereas the low-ORI patients liked both food types equivalently (P < 0.05). After operation (n = 43), both groups showed lower preferences for high-fat potato chips (P < 0.05 for high-ORI group). As anticipated, hunger was dramatically suppressed after RYGB. However, there was more satiety in the high-ORI group (P < 0.05, ANOVA). Most patients undergoing bariatric surgery had a strong familial or genetic component to their disease. RYGB in high-ORI patients was associated with a significant decline in preference of fatty food and a significantly prolonged drop in hunger ratings after a fast and after a standard 282 kcal meal. The success of bariatric surgery may be influenced by the etiology of obesity.