Six conditions are required to benefit from bariatric surgery:

• BMI ≥ 40 kg/m² OR BMI ≥ 30 to 40 kg/m² with at least one comorbidity that is likely to improve following surgery (high blood pressure, obstructive sleep apnoea syndrome, type 2 diabetes, incapacitating joint disorders, non-alcoholic steatohepatitis, etc.)
• failure of medical, nutritional, dietetic and psychotherapeutic treatment that has been properly conducted for six to 12 months (weight loss is not sufficient or weight loss is not maintained)
• multidisciplinary preoperative assessment and management with surgeons, nurse practitioner, dietitians and health psychologists
• patient is well informed
• patient has understood and accepted the need for lifelong surgical and medical follow-up
• acceptable operating risk.

• severe cognitive or mental disorders
• severe and non-stabilised eating disorders
• alcohol or psychoactive substances dependence
• diseases that are life-threatening in the short and medium term
• contraindications to general anaesthesia
• absence of identified prior medical management of obesity and likely inability of the patient to participate in lifelong medical follow-up

• assessment and management of comorbidities (high blood pressure, obstructive sleep apnoea syndrome, type 2 diabetes, incapacitating joint disorders, non-alcoholic steatohepatitis, etc.), assessment of eating behaviour and management of any eating disorder, nutritional and vitamin assessment and correction of any deficits, upper gastrointestinal endoscopy with tests for Helicobacter pylori
• psychological/psychiatric assessment: for all patients who are candidates for obesity surgery
• therapeutic education programme: diet and physical exercise.