Naltrexone/Bupropion With or Without Very Low Calorie Ketogenic Diet for Weight Regain After Bariatric Surgery

Inclusion Criteria: * Participants eligible for inclusion in this Trial must meet all of the following criteria: 1. Voluntary written informed consent of the participant or their legally authorized representative has been obtained prior to any screening procedures 2. Use of highly effective methods of birth control; defined as those that, alone or in combination, result in low failure rate (i.e., less than 1% per year) when used consistently and correctly; such as implants, injectables, combined oral contraceptives, some IUDs, true sexual abstinence (i.e. refraining from heterosexual intercourse during the entire period of risk associated with the Trial treatment(s)) or commitment to a vasectomised partner. 3. Miminum 18 years of age at the time of Informed Consent signature 4. Underwent bariatric surgery (RYGB or SG) with weight regain ≥10% of nadir weight 5. People without Type 2 diabetes (T2D) • No history, no drugs, HbA1c \< 6,5% and FPG \<126 mg/dl) All participants that are considered for Trial participation, per the above criteria will be documented on the Screening Log, including Screen Failures. Exclusion Criteria: * Participants eligible for this Trial must not meet any of the following criteria: 1. Participant has a history of type 2 diabetes mellitus (also drugs, HbA1c \> 6,5% and FPG \>126 mg/dl) 2. IFemale who is pregnant, breast-feeding or intends to become pregnant or is of child-bearing potential and not using an adequate, highly effective contraceptive 3. Participation in an interventional Trial with an investigational medicinal product (IMP) or device 4. Not willing to sign informed consent 5. Younger than 18 years of age at the time of Informed Consent signature 6. Other types of bariatric surgery other than RYGB or SG (including LAGB, BPD) 7. Underwent bariatric surgery (RYGB or SG) with weight regain \<10% of nadir weight 8. Contraindication for VLCKD, including CKD stage 4-5, liver cirrhosis, type 1 diabetes mellitus, active gout 9. Contraindication for NB including the use of opioids, history of CNS tumor or seizures, severe psychiatric disorder or \> 2 psychotropic medications, uncontrolled hypertension 10. Use of other drugs for weight management (e.g. GLP1Ra) in the last 3 months prior to trial intervention 11. Any disorder, which in the Investigator's opinion might jeopardise the participant's safety or compliance with the protocol Participants who meet one or more of the above exclusion criteria must not proceed to be enrolled/randomized in the Trial and will be identified on the Screening Log as Screen Failure.