Bariatric and metabolic surgery has become one of the most important clinical innovations, in 2013 it was selected as top one innovation in medicine by the Cleveland Clinic. The clinical effect of metabolic surgery on the treatment of diabetes is far superior to the medical treatment, traditional diet control methods includes exercise, changing lifestyle and so on, which are almost invalid for severely obese patients, metabolic surgery has become an effective mean of weight loss and metabolic syndrome. In China about 95% of diabetes due to type 2 diabetes, and the ideal control rate is low, metabolic surgery to treat diabetes has become a clinical hot spot. With the bariatric and metabolic surgery guideline promoted in China, more and more problems are exposed gradually; many doctors were confused by the body mass index (BMI) constraints for various guidelines and consensus. So what is the relationship between BMI and bariatric and metabolic surgery-BMI is the most widely measurement index of obesity, but it cannot reflect of the intra fat content totally, so a variety of bariatric and metabolic surgery guidelines were created using BMI as foundation in different regions and countries, in Asia waist circumference was added as an indicator. In metabolic surgery guideline,Asian countries give the lower BMI standard than that in the West, and metabolic surgery indication is different from bariatric surgery, so from the prevention of diabetes complications, American association of clinical endocrinologists and American College of Endocrinology released a new consensus.