This national, prospective, multicenter, and randomized study seeks to evaluate the effect of financial incentives on weight loss in individuals who experience weight regain following bariatric surgery. The study also aims to conduct a cost-utility analysis to measure the effectiveness of the intervention and assess the potential budgetary implications if it were to be implemented on a wider scale.

Our intervention is based on the principle of "contingency management" whereby financial rewards are contingent upon meeting specific weight loss targets. To assess the effectiveness of this approach, patients who have experienced weight regain after bariatric surgery will be randomly assigned to one of three groups. Group 1 will receive the standard care that includes setting a weight-loss target based on the weight achieved at 12 months post-bariatric surgery following the standard multidisciplinary follow-up at the inclusion center. Group 2 will receive the same treatment as the control group (Group 1), but with an additional financial incentive if the weight loss target (corresponding to the weight they reached 12 months after bariatric surgery) is achieved 12 months after inclusion. Group 3 will receive the same treatment as the control group (Group 1), but the financial incentive will be proportional to the actual weight loss achieved relative to the weight loss target (corresponding to the weight they reached 12 months after bariatric surgery).

The study will include a standard post-bariatric surgery follow-up visits scheduled at 6, 12, 18, and 24 months, as per routine practice. At the 12-month visit, participants will be eligible to receive a financial incentive based on their arm assignment and the extent of weight loss achieved. After the 12-month visit, participants will not receive any additional financial incentives until the 24-month visit.

Inclusion Criteria:

• Male or female over 18 years of age
• Patients with a history of adjustable gastric banding, sleeve gastrectomy, gastric bypass or SADI-sleeve surgery
• Patient with a post-operative delay of more than 2 years
• Patient who has gained ≥10% of the maximum weight lost
• Patient still obese (body mass index ≥ 30 kg/m²) after surgery

Exclusion Criteria:

• Pregnant women
• Women of childbearing potential planning a pregnancy during the first year of the study
• Persons under legal protection (safeguard of justice, guardianship, curatorship, etc.)

Individual participant data (IPD) that underlie results in publication could be shared. IPD detailed in the protocol of a planned metaanalysis could be shared.

Two years after the last publication

Data sharing must be accepted by the sponsor and the PI based on a scientific project and scientific involvement of the PI team. Collaboration will be fostered.

Teams wishing obtain IPD must meet the sponsor and IP team to present scientifics (and commercial) purpose, IPD needed, format of data transmission, and timeframe. Technical feasibility and financial support will be discussed before mandatory contractualization.

Processing of shared data must comply with European General Data Protection Regulation (GDPR).