This is a prospective, 24-month, longitudinal study of patients planning to undergo bariatric surgery (Roux-en-Y Gastric Bypass or Sleeve Gastrectomy) in which we aim to identify correlates and predictors of observed weight loss trajectories following bariatric surgery. This approach will expand current knowledge by examining the combined impact of empirically supported behavioral and biological data in a large sample over time. Intensive measurement of problematic eating behaviors, mood, and compliance with diet and exercise regimens post-surgery will be analyzed in the context of lterations in parallel with, or in response to, changes observed in the gut microbiota. Identifying these post-surgical predictors of weight loss and comorbidity resolution will allow for the development of individualized interventions to optimize surgery-related outcomes.

Inclusion Criteria:

1. In evaluation for Roux-en-Y Gastric Bypass or Sleeve Gastrectomy.
2. Age 18-65, inclusive

Exclusion Criteria:

1. Alcohol or substance use disorder in past year
2. Severe psychiatric disorder that may affect ability to complete the protocol
3. Regular tobacco use during the last year
4. Current medication taken routinely and known to impact factors that may affect the gut microbiome
5. Use of any oral or injectable antibiotic in the past month
6. Use of commercially available pre/pro biotic in the past month
7. History of significant disease/disorder that would be expected to impact the microbiome of the gut
8. Inability to engage in physical activity or dietary monitoring
9. Nonprescribed/illicit drug use
10. Pregnant or breastfeeding

Participants planning to undergo Roux-en-Y Gastric Bypass or Sleeve Gastrectomy.

To the extent required by NIH and permitted by appropriate laws and rules. It will be available after the conclusion of the study and when the data have been cleaned.