Obesity is a chronic multifactorial disease with inflammatory characteristics that affects both sexes and all ages worldwide, increasing morbidity and mortality from various diseases. Obesity is associated with dysbiosis of the gut microbiota, thereby altering nutrient absorption and energy metabolism. Bariatric surgery has proven to be the best treatment for morbid obesity and diseases associated with overweight. Studies of the effects of bariatric surgery on the gut microbiota conducted in the last five years were characterized by a small number of subjects in the samples and a follow-up between 6 months and 1 year, with heterogeneous results. In general, bariatric surgery produces important changes in the intestinal microbiota, with an increase in Proteobacteria, Fusobacteria and Verrucomicrobia phyla; and decrease of the phylum Firmicutes. Akkermansia muciniphila it can be a key bact...