A double-blinded, randomised, placebo-controlled trial of semaglutide 3.0 mg/ml in patients with poor weight-loss following bariatric surgery. The primary aim of this trial is to determine whether, and the extent to which, 68 weeks of subcutaneous semaglutide 3.0 mg/ml causes greater percentage weight loss (%WL), reduction in adiposity, improvement in metabolic and inflammatory indices and health-related quality of life (HRQoL) than placebo, in patients with poor weight loss following gastric bypass or sleeve gastrectomy.

Inclusion Criteria:

1. Patients, ≥1 year primary GB or primary SG, with poor weight-loss (<20% WL) that is not caused by either a surgical or psychological problem.
2. Adults, 18-65 years inclusive.
3. Females of childbearing potential and female partners of male participants must be willing to use highly effective method of contraception (hormonal or barrier method of birth control; abstinence) (Appendix 2) from the time consent is signed until 2 months after treatment discontinuation.
4. Females of childbearing potential must have a negative pregnancy test within 7 days prior to randomisation. NOTE: Subjects are considered not of child bearing potential if they are surgically sterile (i.e. they have undergone a hysterectomy, bilateral tubal ligation, or bilateral oophorectomy) or they are postmenopausal.
5. A self-reported ≤5 % variation in body weight over preceding 3 months.
6. Fluent in English and able to understand and complete questionnaires.
7. Participants capable to provide written informed consent and comply with the trial protocol.

Exclusion Criteria:

1. Bariatric surgical procedure other than GB and SG, or revision bariatric surgery of any operation type.
2. Personal history of type I diabetes or type II diabetes mellitus currently treated with insulin.
3. Concomitant use of GLP-1R agonist or DPPIV-inhibitors.
4. Female who is pregnant, breast-feeding, or intends to become pregnant.
5. Current participation in other clinical intervention trial.
6. History of suicidal attempt in the previous 5 years or untreated severe depression or mental health condition assessed by direct questioning.
7. Symptomatic gallstone disease
8. Uncontrolled hypertension (systolic blood pressure ≥ 160 mmHg or diastolic blood pressure ≥ 100 mmHg).
9. Renal impairment measured as glomerular infiltration rate (eGFR <15 ml/min 1.73 m2
10. Known or suspected hypersensitivity to semaglutide or any of the excipients involved in their formulation.
11. Personal or family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndrome type 2.
12. History of malignant neoplasms within the past 5 years prior to screening. Basal and squamous cell skin cancer and any carcinoma in-situ are allowed.
13. Personal history of acute pancreatitis 180 days before screening or chronic pancreatitis.
14. Uncontrolled thyroid disease.
15. History of stroke, unstable angina, acute coronary syndrome, congestive heart failure New York Heart Association class III-IV within the preceding 12 months.
16. Untreated clinically significant arrhythmias.
17. Diabetic gastroparesis.
18. Concomitant usage of medications that cause weight gain or weight loss.
19. Known or suspected abuse of alcohol or recreational drugs.
20. Severe hepatic impairment diagnosed via liver function blood tests and clinical evaluation
21. Any additional factor, which in the investigator's opinion, might jeopardise the subject's safety or compliance with the trial protocol.

double blinded: both participants and study doctors will be blind to group allocation