Inclusion Criteria:  Men and women between 18 and 65 years BMI ≥35 kg/m2 and at least one severe obesity-related complications, or BMI ≥40 kg/m2 Undergoing Roux-en-Y gastric bypass Willing to take a probiotic/placebo supplement twice a day for 60 days Willing and able to provide written informed  Exclusion Criteria:  Intake of antibiotics and/or probiotics in the previous 12 weeks Weight change >5% in the previous 12 weeks Diagnosis of gastrointestinal disease or other significant illness Pregnancy or breastfeeding