Dietary Sugar Absorptive Phenotype for Prediction of Weight Loss Outcome

Inclusion Criteria: \- Obese patients (BMI ≥ 30) scheduled for BS undergoing standard of care screening EGD, or lean BS-naïve individuals (BMI ≤ 25) subjected to EGD for routine clinical indications as part of standard care. Exclusion Criteria: * Adults unable to consent, including non-English speakers. * Pregnant women because endoscopy is a risk factor. All patients of childbearing age undergo history as well as urine pregnancy test as a standard of care prior to undergoing endoscopy as the procedure is performed under anesthesia. * Prisoners. * Subjects with preexisting conditions (e.g., bleeding at the time of the procedure, suspected perforation during the standard-of-care procedure) will be excluded from the study at the time of the endoscopy. * Have a contraindication to endoscopy. * A history of surgery on the stomach or small intestine. * Type 1 diabetes (clinical diagnosis and/or positive glutamic acid decarboxylase antibodies). * Using weight loss medications. * Active malignancy within the last 5 years.