The intestinal immune response could play an important role in obesity-related comorbidities. We aim to study the profile of duodenal cytokines and chemokines in patients with morbid obesity (MO), its relation with insulin resistance (IR) and the intake of metformin, and with the evolution of MO after sleeve gastrectomy (SG). In our work there is an association between a higher IR and a lower duodenal immune response in MO, with a slight increase in those patients with metformin treatment. Intestinal immune response could be involved in the evolution of BMI after SG.