Inclusion Criteria:  Age greater than 18 Body mass index of 40-60 kg/m2 Meet insurance criteria, as set forth by the patient's insurance policy, to qualify for coverage for weight loss surgery Planned laparoscopic Roux-en-Y gastric bypass Willingness to have blood collected before and after surgical procedure at defined points and collect and mail stool sample before operation and at defined post-operative time points.  Exclusion Criteria:  Age less than 18 Patient fails to fulfill insurance mandated criteria Unwilling to be randomized to variable length to gastric bypass or unwilling to have blood collected or personally collect and mail in stool sample Unwilling to follow-up at required postoperative visits