Premature termination due to lack of inclusion. Behavioral preparation is perceived as too restrictive by patients. Furthermore, the Covid and post-covid period has drastically restricted the possibilities of support for behavioral preparation.

Prospective randomized clinical trial aiming to compare a comprehensive, intensive behavioral lifestyle intervention and usual care during the preoperative preparation to bariatric surgery, with primary outcome on excess weight loss and secondary outcomes on patient's physical status, quality of life, comorbidity and technical difficulty of the surgery.

Obesity is a complex, multifactorial pathology that has major public health importance. Lifestyle modification is the cornerstone of all obesity treatments, including surgery. Throughout the non-surgical treatment options, high-intensity, on-site comprehensive lifestyle intervention has demonstrated the best efficacy in obtaining weight loss, but with a risk of progressive weight regain, after 6 months (1). In obese adults, bariatric surgery produces greater weight loss and weight loss maintenance than the conventional medical treatment and lifestyle intervention (1).

There is no consensus on whether combining these two approaches (i.e. high-intensity, on-site comprehensive lifestyle intervention and bariatric surgery) results in enhanced weight loss or more sustainable outcomes. The present randomized trial aims to answer this question.

Patients preparing for bariatric surgery will be randomized between two groups. The first group will receive the usual care as recommended by the French Health Authority ("Haute Autorité de santé"), including 6 months of endocrine and nutritional follow-up and educational intervention. The second group will receive a high-intensity, 4 weeks on-site comprehensive lifestyle intervention, including prescription of a moderately reduced-calorie diet, a program of increased physical activity, and behavioral management. The patients from both groups will then be operated on and followed for at least 2 years. Complete work-up, including clinical examination, comorbidity assessment, MRI of the liver, thigh and abdominal fat, 6 minutes' walk test, quality of life questionnaires will be performed at the begging of the follow-up, after the preparation (usual care or intensive) and 2 years after surgery. Clinical and biological assessment will be performed regularly after surgery, and technical details from the bariatric interventions will be analyzed in order to assess the eventual facilitation of the gestures in the intervention group.

Inclusion Criteria:

• Patient with a BMI (Body Mass Index) of 40 or BMI of 35 with associated comorbidity and who desires obesity surgery
• Patient agreeing to participate in the study, including the 2 years follow-up
• Patient accepting the constraints of the study related to the group to which he/she will be assigned as a result of randomization (availability to his work, his family, etc.)
• Patient able to receive and to understand the study information and to give written informed consent
• Patient affiliated with the French social security system

Exclusion Criteria:

• Patient with a BMI of more than 60

• Patient with contraindication to laparoscopic obesity surgery

• Patient already operated on for obesity

• Patient with a history of major abdominal surgery

• Patient with contraindications to MRI:

  • pace maker or automatic defibrillator, implanted insulin pump
  • auditory neurostimulator, anal neurostimulator, etc.
  • ferromagnetic bodies in soft tissues, intraocular foreign bodies, cerebral vascular clips
  • claustrophobia
  • morphotype not allowing access to MRI: morbid obesity with waist circumference greater than 150 cm, shoulder width greater than 59 cm

• Patient with psychiatric pathology (untreated psychosis, drug dependence, etc.)

• Pregnant or breast-feeding patient

• Patient in periods of exclusion (determined by a previous or ongoing study)

• Patient under safeguard of justice

• Patient under guardianship