In order to investigate how gut microbiota interventions are able to change gut microbiota population and impact insulin resistance, 30 type2 diabetes volunteers with obesity will be randomized to one of the three treatment groups: 1) probiotics arm, who will take a Lactobacillus fermentum D3 in pills daily; 2) FMT arm, who will take a lyophilized fecal microbiota transplant in pills; and 3) control group, who will take placebo pills. After 3 months, insulin resistance, glucose metabolism parameters, and gut microbiota variation will be assessed.

Inclusion Criteria:

• Type2 diabetes in treatment with metformin
• 30 kg/m2≤IMC≤40 kg/m2
• 30-70 years old
• HOMA-IR >6
• Informed consent

Exclusion Criteria:

• psychopathologic alterations that do not permit the adherence to the trial.
• Diabetes medication different from metformin.
• History of cholecystectomy.
• Use of Probiotics, and/or antibiotics in the last 3 months