Type 2 Diabetes Mellitus (DM) is one of the relevant changes observed in Metabolic Syndrome (MS), which in turn is inherent to obesity. In extreme cases of obesity, bariatric surgery is indicated, reflecting directly on weight loss and improving metabolic rates. Scientific studies show a clinical improvement in glycemic values a few days after surgery, which disassociates the improvement presented, from the weight loss condition. The reversal of type 2 diabetes would be associated with changes in the entero-insular axis resulting from duodendo-jejunal exclusion, which would trigger an increase in the production of incretins such as GLP1 (Glucagon-like peptide-1) and a decrease in GIP (glucose-dependent insulinotropic polypeptide) reflecting directly in the body's sensitization to insulin. A bibliographic survey was carried out through scientific articles searched on the various research platforms such as Scielo and Google academic to verify the real causes of the clinical improvement of post-bariatric glycemic indexes. The restructuring of the gastrointestinal tract excluding the jejunal duodenum facilitates the action of incretins, modulating their production and improving metabolic rates. The gastroplasty with the best therapeutic results for DM was Roux Y derivation, but the patient must undergo changes in habits, such as healthy eating and physical activity.