Probiotic Supplementation on Weight Loss

The investigators are interested in seeing how a probiotic, which is a dietary supplement containing large amounts of 'good' bacteria, can influence the make-up of the gut bacterial population and what effect it has on weight loss and loss of fat. Before undergoing weight loss surgery (sleeve gastrectomy or roux-en-y gastric bypass), study participants will be asked to provide a stool sample to assess the make-up of their gut bacterial population. They will also undergo a limited CT scan of the abdomen and DEXA (Xray) to help assess the amount of fat present inside the body.

After undergoing weight loss surgery (sleeve gastrectomy or roux-en-y gastric bypass), study participants will be given either a probiotic supplement or dummy pill (placebo) for 3 months, in addition to all usual care that occurs after surgery. The CT scan, DEXA scan and stool sample will be repeated at the end of the 3 month period and analyzed for changes.

Inclusion criteria

• All subjects who are > 18 and < 65 years of age recruited from the Mayo Clinic bariatric surgery clinic
• Will also meet one of the National Institute of Health's criteria for bariatric surgery, i.e. body mass index (BMI) > 40 kg/m2 or BMI > 35 kg/m2 with significant weight-related comorbidities.
• Patients will be eligible if they are not on chronic antibiotic therapy and without active systemic illness.

Exclusion criteria

• Patients with type 1 or 2 diabetes will be excluded due to the known pre-existing changes in the gut microbiome in this population. All patients will not have had exposure to probiotics, prebiotics or antibiotics in the preceding 4 weeks.
• Patients with allergy to antibiotics precluding the use of standard peri-operative antibiotics (cefazolin and metronidazole) will be excluded.