**1. Introduction**

Obesity has become a major public health problem with an undeniable impact on overall well-being and survival given its association with multiple diseases such as diabetes mellitus, cardiovascular disease, and various malignancies among others [1, 2]. Bariatric, or metabolic surgery, is the most effective current treatment for obesity, resulting not only in significant weight reduction but also significant improvement and even remission of several of these comorbidities [3, 4]. It has been shown that these benefits are related to both, the anatomical rearrangement, and the changes in gut physiology. Each segment of the gastrointestinal tract has a different influence on the metabolic pathways; thus, clinical outcomes differ among the divergent surgical procedures. When duodenal exclusion (DE) is performed, caloric restriction, diversion of the proximal small bowel, changes in nutrient absorption, and effects on gastrointestinal tract hormones are underlying mechanisms that lead to such favorable results. The contribution of each of these factors to weight reduction and metabolic amelioration varies according to the type of surgery. Since diabetes mellitus along with obesity has become one of the leading health problems worldwide, the process for the favorable effects of this group of procedures in the mitigation of hyperglycemia and even resolution of diabetes mellitus type 2 (T2DM), has been

widely studied. Changes in bile acid circulation and metabolism, incretins and possible anti-incretins, gastrointestinal nutrient-sensing and metabolization, glucose and energy homeostasis, as well as mediators of the intestinal microbiome, are all weightindependent factors believed to be related to these antidiabetic outcomes. However, although the beneficial effects regarding weight loss and metabolic improvement, the gastric acid reduction and/or hypoabsorption associated with surgeries involving DE led to significant nutrient deficiency and, if not treated, long-term complications.
