This study is trying to determine whether the success of bariatric surgery can be predicted by evaluating the dietary sugar absorptive characteristics in the small intestine and if there is any gene expression change on the dietary sugar absorptive characteristics.

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.

Obese patients scheduled for bariatric surgery (BS) (both men and women of any racial/ethnic background), or lean BS-naïve subjects presenting for surveillance/screening endoscopy procedure as part of their standard medical care (controls).