The study will be conducted in the following population: obese patients with normal glucose tolerance (HbA1c ≤ 5.6%, n=12), pre-sugar patients (5.7% ≤ HbA1c ≤ 6.4%, n=18) and patients with T2DM (HbA1c ≥ 6.4% , n=18). After recruiting, they were followed up at 1, 3, 6, and 12 months postoperatively, and their preoperative and follow-up examination values related to demographics, body composition, blood biochemistry, and glucose metabolic balance, as well as quantitative MRI imaging and oral glucose tolerance test (OGTT) will be collected. An interim analysis will be performed at 6 months postoperatively and overall analysis will be performed at 12 months postoperatively by descriptive statistics and ANOVA methods to explore the effect of adiposity on the progression of diabetes mellitus and insulin secretory function.

The study will be conducted in the following population: obese patients with normal glucose tolerance (HbA1c ≤ 5.6%, n=12), pre-sugar patients (5.7% ≤ HbA1c ≤ 6.4%, n=18) and patients with T2DM (HbA1c ≥ 6.4% , n=18). After recruiting, they were followed up at 1, 3, 6, and 12 months postoperatively, and their preoperative and follow-up examination values related to demographics, body composition, blood biochemistry, and glucose metabolic balance, as well as quantitative MRI imaging and oral glucose tolerance test (OGTT) will be collected. An interim analysis will be performed at 6 months postoperatively and overall analysis will be performed at 12 months postoperatively by descriptive statistics and ANOVA methods to explore the effect of adiposity on the progression of diabetes mellitus and insulin secretory function.

Inclusion Criteria:

• BMI ≥ 28 kg/m2, meeting the indications for surgical weight loss surgery (gastrectomy)
• Normal glucose tolerance group: HbA1c ≤ 5.6%; ≥ 6 cases aged 24 years or above
• IGT patients: 5.7% ≤ HbA1c ≤ 6.4%; ≥ 12 cases aged 24 years or above
• T2DM patients: Subjects with HbA1c ≥ 6.4% or HbA1c well controlled by medication can be diagnosed as T2DM based on self-reported or fasting/postprandial blood glucose diagnosis; ≥ 12 cases aged 24 years and above.
• Between the ages of 16 and 65 (inclusive), with no less than one-third of either gender
• The subjects understand the content of the informed consent form and voluntarily sign it, which allows them to maintain good communication with the researchers and comply with the requirements of the clinical trial

Exclusion Criteria:

• Type I diabetes patients (autoimmune diabetes patients with T1DM antibody)
• Suffering from special types of diabetes, including cortisolism, growth hormone tumor, glucagon tumor and diabetes caused by some genetic factors
• Significant weight loss occurred before enrollment (>3% weight loss in the first 3 months)
• Participated in other research projects as a subject within 6 months prior to screening
• Donate or lose ≥ 400 mL of blood within 8 weeks prior to screening
• Regular use (cumulative use for 3 months in the past 12 months) or treatment with corticosteroids, contraceptives, thiazide diuretics, and quinolone antibiotics in the past two months
• Regular use (cumulative use for 3 months in the past 12 months) or treatment with anti obesity drugs in the past two months
• The following hypoglycemic drugs have been used routinely (for 3 months accumulatively in the past 12 months) or in the past two months: sulfonylureas (glibenclamide, glipizide, gliclazide, gliquidone, glimepiride, etc.), non sulfonylureas (repaglinide, nateglinide, migglinide, etc.), GLP-1 receptor agonists (exenatide, lilalutide, etc.) DPP-4 inhibitors (sigliptin, alogliptin, vildagliptin, shagliptin, linagliptin, etc.) or glucokinase agonists (doegliptin, etc.)
• Contraindications to magnetic resonance imaging
• The risk of complications significantly increases during the perioperative or postoperative period
• Those with a history of other weight loss surgeries
• Individuals with a history of cardiovascular surgery and severe cardiovascular and pulmonary diseases: including stroke, severe coronary heart disease, arrhythmia, unstable angina, myocardial infarction within 6 months, peripheral vascular disease, heart failure, and uncontrolled hypertension
• Clinically significant history of ECG abnormalities or family history of long QT syndrome (grandparents, parents, brothers and sisters)
• People with a history of kidney disease: have a history or evidence of renal insufficiency, manifested as clinically significant creatinine abnormalities or urinary composition abnormalities (such as tubular abnormalities), or eGFR<60 ml/min/1.73m2
• Patients with a history of gastrointestinal surgery (excluding appendectomy and cholecystectomy), inflammatory bowel disease, esophageal disease, including severe refractory esophagitis, Barrett's disease, esophageal motility disorders, or other gastric motility impairments, or those with esophageal hiatal hernia>3cm in size, chronic or acute bleeding, including peptic ulcer disease, portal hypertension (gastric or esophageal varices), chronic pancreatitis or cirrhosis
• Individuals with a history of eating disorders or mental illness
• Individuals with a history of infectious diseases are excluded if they have any of the following: human immunodeficiency virus (HIV) antibodies, hepatitis B surface antigen (HBsAg), hepatitis C virus (HCV) antibodies, or those who have tested positive for syphilis
• Smokers, those who smoke more than 10 cigarettes or equivalent amounts of tobacco per day and cannot stop smoking during the trial period
• There is a history of drug or alcohol abuse within the 12 months prior to the trial, or evidence of such abuse is found during laboratory examinations during the screening period evaluation
• Women who are pregnant, breastfeeding, or planning to conceive and are unwilling to use contraception during the trial period
• Malignant tumor patients
• The researcher believes that it is not suitable for participants in the experiment
• For different types of subjects, additional exclusion criteria: obese patients with normal glucose tolerance: fasting blood glucose ≥ 7.0 mmol/L or ≤ 3.9 mmol/L (excluding diabetes and hypoglycemia)
• Obese patients before glucose: fasting blood glucose ≥ 7.0 mmol/L or ≤ 3.9 mmol/L (excluding diabetes and hypoglycemia)
• Obese T2DM patients: Fasting blood glucose ≤ 3.9 mmol/L (excluding those with hypoglycemia)

Obese people who will undergo sleeve gastrectomy in Peking University Third Hospital and meet the admission criteria.