Inclusion Criteria:
1. Aged 18 years or older, or subjects who have reached the legal age for signing informed consent in accordance with local laws and regulations.
2. BMI ≥ 32.5 kg/m²; or BMI ≥ 27.5 kg/m² combined with type 2 diabetes mellitus (regardless of the effectiveness of medical treatment for type 2 diabetes); or BMI between 27.5 kg/m² and 32.5 kg/m² with ineffective medical weight loss or combined with other obesity-related diseases for which medical treatment is ineffective.
3. Willing to comply with the long-term strict dietary restrictions required by the surgery.
4. Capable of providing informed consent, able to complete all routine follow-up visits, and willing to abide by the protocol requirements, including signing the informed consent form, completing relevant examinations, and receiving dietary counseling.
5. Females of childbearing potential (i.e., premenopausal or not sterilized) must agree to use adequate contraceptive measures.
Exclusion Criteria:
1. History of foregut or gastrointestinal (GI) surgery (except uncomplicated cholecystectomy or appendectomy)
2. Prior gastrointestinal surgery with sequelae, i.e. obstruction, and/or adhesive peritonitis or known abdominal adhesions.
3. Prior open or laparoscopic bariatric surgery.
4. Prior surgery of any kind on the esophagus or any type of hiatal hernia surgery.
5. Any inflammatory disease of the gastrointestinal tract including severe (LA Grade C or D) esophagitis, gastric ulceration, duodenal ulceration, specific inflammation such as Crohn's disease, and the doctor judges that it may affect the operation or efficacy of ESG.
6. Potential upper gastrointestinal bleeding conditions such as esophageal or gastric varices, congenital or acquired intestinal telangiectasis, or other congenital anomalies of the gastrointestinal tract such as atresia or stenosis.
7. History of gastrointestinal stromal tumors, gastrointestinal cancer, low-grade or high-grade gastric intraepithelial neoplasia, or familial or non-familial adenomatous polyposis syndrome.
8. Gastric masses or untreated gastric polyps with a diameter \> 1 cm.
9. Hiatal hernia (Z-line displacement above the diaphragm \> 4 cm) or severe/refractory gastroesophageal reflux symptoms, which the physician judges may affect the performance or prognosis of ESG.
10. Structural abnormalities of the esophagus or pharynx that may impede endoscopic passage (e.g., strictures or diverticula), which the physician judges may affect the performance or prognosis of ESG.
11. Gastrointestinal motility disorders (e.g., achalasia, severe esophageal motility disorders, gastroparesis, or intractable constipation), which the physician judges may affect the performance or prognosis of ESG.
12. Evidence of untreated psychiatric or eating disorders, such as major depression, schizophrenia, substance abuse, binge eating disorder, or bulimia nervosa.
13. Coagulopathy with INR \> 1.5 that cannot be corrected (per physician's judgment) or requirement for continuous full anticoagulant therapy, and/or any underlying diseases associated with high bleeding risk.
14. Insulin-dependent diabetes mellitus (type 1 or type 2), or high likelihood of requiring insulin therapy within the next 12 months.
15. Decompensated cirrhosis, or acute/chronic liver dysfunction that the physician judges make the subject unsuitable for ESG treatment.
16. Diagnosis of autoimmune connective tissue diseases (e.g., systemic lupus erythematosus, scleroderma) or immunocompromise, which the physician assesses may affect the performance or prognosis of ESG.
17. Known history of endocrine diseases affecting body weight (e.g., Cushing's syndrome, uncontrolled hypothyroidism, or hyperthyroidism), which the physician assesses may affect the performance or prognosis of ESG.
18. Anemia: Hemoglobin (Hgb) \< 110 g/L for females; Hgb \< 120 g/L for males.
19. Any other medical conditions precluding elective endoscopy, such as poor general health, history of severe renal, hepatic, cardiac, and/or pulmonary diseases, and/or severe or uncontrolled psychiatric illnesses or abnormalities that may impair the patient's ability to understand or comply with follow-up visits and lifestyle interventions.
20. Active psychological issues as determined by a psychologist or psychiatrist, precluding participation in lifestyle modification programs.
21. Unwillingness to participate in the established medically supervised dietary and behavioral modification programs, as well as routine medical follow-up.
22. Daily treatment with prescribed high-dose aspirin (\> 80 mg per day), non-steroidal anti-inflammatory drugs (NSAIDs), antiplatelet agents, anticoagulants, corticosteroids, immunosuppressants, or other gastric irritant medications.
23. Interval use of medications that may be affected by changes in gastric emptying (e.g., antiepileptic drugs or antiarrhythmic drugs).
24. Inability or unwillingness to take prescribed proton pump inhibitor (PPI) medications.
25. Current use of weight loss medications or other weight loss devices or use within the past 90 days.
26. Current participation in a clinical trial involving investigational drugs or devices, or participation in such a trial within 30 days prior to enrollment in this study.
27. Use of intragastric devices within 30 days prior to this study, which the physician assesses may affect the performance or prognosis of ESG.
28. Unwillingness to avoid any reconstructive and/or plastic surgeries that may affect body weight during the study (e.g., mammoplasty, liposuction).
29. Other conditions deemed unsuitable for endoscopy or ESG treatment by the investigator, including but not limited to conditions that the investigator believes may expose the subject to significant risks, confound study results, increase risks associated with endoscopy and/or endoscopic procedures, or substantially interfere with the subject's participation in the study.
30. Pregnancy, lactation, or intention to become pregnant during the study (for females of childbearing potential).
