<qa>  What is the purpose of this study?In fact, clinical and translational studies over the last decade have shown that a number of gastrointestinal mechanisms, including changes in gut hormones, neural signalling, intestinal flora, bile acid and lipid metabolism can play a significant role in the effects of this procedure on energy homeostasis. This is a long-term follow-up and interventional study in individuals who have been diagnosed with moderate to severe obesity with or without diabetes. The purpose of this study is to determine the effects of SG on weight and blood sugar control and underlying mechanisms by metabolomics, metagenomics, functional magnetic resonance imaging fMRI ,adipose tissue expression chip and etc. 