This study will enroll type 2 diabetes mellitus patients follwing Roux-en-Y gastric bypassing surgery and obese persons without type 2 diabetes surgery. The defferent expressions of serum proteins of obese persons without type 2 diabetes and type 2 diabetes patients following gastric bypassing surgery after 10 days or 3 months were detected by serum proteomics. Blood samples and urine will be taken prior to surgery, 10 days after surgery and 3 months after surgery. The long term prognosis of diabetes mellitus for 1 years and the remission rate of diabetes of patients will be evaluated.