In this study, it is aimed to evaluate whether the addition of prebiotics to patients' post-operative diets increases Roux-en-Y Gastric Bypass surgery effects. Half of the participants were randomized prebiotic with conventional yogurt, while the other half were randomized only conventional yogurt as a snack

Following bariatric surgery, positive alterations are observed in gut microbiota, intestinal peptides, and inflammatory cytokines. Previous studies demonstrate that prebiotic use alone in a tolerable dose (which is 10 g/day) among obese, overweight, or diabetic individuals accelerated the weight loss by reducing hunger and food intake. Furthermore, it could also contribute to the improvement of glucose homeostasis by increase postprandial PYY and GLP-1 levels. Prebiotics feeds healthy intestinal bacteria and enhances their positive effects. The present positive effects appear with SCFAs that stimulates PYY and GLP-1 release and produced by fermentation of prebiotics by bacteria. From this point forth, it was hypothesized that post-operative pre-probiotic usage may enhance the effects of Roux-en-Y Gastric Bypass (RYGB). In addition, administration of pre-probiotics following RYGB may be considered as a simple and cheap treatment support, especially for protecting patients with poor medicine compliance against nutritional deficiencies, as well as for diabetic patients whose glucose regulations deteriorate in the long term, and for those who regain weight.

With the result that the effects of prebiotic supplementation on metabolic results of RYGB surgery in this prospective, randomized, controlled study with a duration of 24 weeks were tested.

Inclusion Criteria:

• BMI >40kg/m2; perform of other types of bariatric surgery except gastric bypass (i.e. sleeve gastrectomy, adjustable gastric band)

Exclusion Criteria: I

• Administration of antibiotics (other than 1 g ampicillin-sulbactam one hour before surgery), the presence of chronic gastrointestinal, liver or kidney diseases and malignancy.