Morbid obesity (BMI>40 kg/m2) is a challenging health condition with an increasing incidence in the last decades. Conventional therapy which consists in diet and lifestyle interventions, along with pharmaceutical therapy, has a limited effect on morbidly obese patients. In this context, bariatric surgery is the most effective approach, leading to significant weight loss, along with other beneficial effects like type 2 diabetes resolution or improvement of cardiovascular status. The bariatric surgery outcomes can widely vary among individuals, with a significant percentage of patients having small benefits from the operation. These variations may be partially explained by the genetic background of each individual. During the last years, several studies have been conducted in order to determine the genetic and epigenetic factors involved in bariatric surgery outcomes. Many genes involved in different molecular pathways were found to be associated with weight loss after bariatric surgery. Epigenetic studies revealed that genes methylation may be influenced by weight loss interventions. All these findings suggest that there is an intimate connection between genetic and epigenetic factors and the bariatric surgery outcomes. Further studies are required in order to better understand if genetics can be used in order to predict the operation results.