Obesity increases the risk of developing or worsening many disorders particularly type 2 diabetes, a difficult-to-control chronic disease, treated with different drugs even with insulin, frequently without reaching therapeutic goals neither reducing cardiovascular risk. Therapy becomes more complex when type 2 diabetes is associated with severe obesity. The use of bariatric and metabolic surgery in patients with severe obesity and diabetes is assessed, and the different surgical techniques, assumptions about its mechanism of action, selection of patients and results are also reviewed. Bariatric surgery has proven to be effective in the treatment of severe obesity and type 2 diabetes in patients with BMI >35 kg/m2. This type of surgery has shown to be acceptable and well tolerated in selected and low risk patients capable of treatment Bariatric surgery has sufficient scientific evidence in these patients. However, there is no strong evidence of metabolic surgery in patients with BMI <35 kg/m2 and even with BMI <30 kg/m2. Preliminary data shows promising results in the short and intermediate term, but there is no sufficient evidence available supporting its indication in these patients. More research is needed to establish the efficacy and safety of these surgical techniques in the long term.