This prospective, single arm, longitudinal study aims to assess the effect of bariatric surgery on glucose metabolism and kidney function.

In recent years, it has become apparent that bariatric surgery not only promote dramatic weight loss but improve or eliminate type 2 diabetes (T2D). Furthermore, it has become increasingly clear that glucose homeostasis, which is mainly determined based on insulin secretion and insulin resistance, improves through mechanisms additional to the secondary consequences of weight reduction. We aims to assess the effect of bariatric surgery on glucose control and kidney function, and excavate potential mechanism for those effects.

Inclusion Criteria:

• ≥20 years old
• body mass index ≥27.5 kg/m2, in case of type 2 diabetes
• body mass index ≥35 kg/m2, in case of non-type 2 diabetes

Exclusion Criteria:

• Prior complex gastrointestinal surgery, including that of the stomach, small intestine, large intestine, bile duct, pancreas, and spleen; Nissen, and trauma (except hemorrhoidectomy, herniorrhaphy, and appendectomy)
• Abdominal, thoracic, pelvic, and/or obstetric-gynecologic surgery within 3 months or at the discretion of the Investigator
• Cardiovascular conditions including significant known coronary artery disease (CAD), uncompensated congestive heart failure, history of stroke, or uncontrolled hypertension (defined as medially treated with the mean of three separate measurements systolic blood pressure >180 mmHg or diastolic blood pressure >110 mmHg).

Subjects with CAD who were successfully treated with coronary artery bypass graft or percutaneous coronary intervention within 3 months and who have no evidence of active ischemia are eligible

• Kidney diseases including renovascular hypertension, renal artery stenosis, or end-stage renal disease
• Known history of chronic liver diseases including liver cirrhosis and alpha-1-antitrypsin deficiency
• Gastrointestinal disorders including a known history of celiac disease or any other malabsorptive disorders or inflammatory bowel disease (Crohn's disease or ulcerative colitis)
• Psychiatric disorders including dementia, active psychosis, history of suicide attempts, and alcohol or drug abuse within 12 months
• Severe pulmonary disease defined as forced expiratory volume at one second <50% of the predicted value
• Anemia defined as hemoglobin <8 in females and 10 in males
• Malignancy within 5 years (except squamous cell and basal cell cancer of the skin). Subjects diagnosed with early or stage 1 cancer that was successfully treated are eligible based on the Investigator's discretion
• Any condition or major illness that in the Investigator's judgement places the subject at undue risk by participating in the study
• Pregnancy
• Unable to understand the risks, realistic benefits, and compliance requirements of each program
• Use of investigational therapy or participation in any other clinical trial within 3 months
• Plans to move outside South Korea within the next 2 years