Eighteen (18) subjects with and fourteen (14) subjects without T2DM (total 32 subjects), who have been scheduled to undergo RYGBS as standard of care, will be recruited. For each enrolled subject, data collection will include an intestinal tissue sample (Roux limb tissue sampling from discarded tissue) at the time of RYGBS, from the mucosa of the jejunum, within 40 cm from the gastrojejunal anastomosis. Postoperatively, tissue sampling from the same area will be performed by an Upper GI endoscopy, at 1 month (±15 days), 6 months (±1 month) and 12 months (±2 months) after RYGBS. Tissue samples will be processed for histo-morphological examination and for RNA, protein and metabolomics analyses. A blood sample will be obtained at all time points and analyzed for metabolic biomarkers. Data analysis will include description and comparison of the morphological, gene protein and metabolite signatures of the intestinal (Roux limb) tissue and the blood biomarkers from each time point. Additionally, these outcome measures will be compared between the two groups (T2DM and Non-T2DM). Finally, a correlation of the intestinal adaptive changes with metabolic status, some eating behaviors, adverse symptomatology, and quality of life will be undertaken.