The main objective of this study is to identify changes in eating behaviors and physical activity in patients after bariatric surgery and their family members living in same household: children aged between 11-17 years, spouse, parents, cohabitee or partner in a civil union.

As secondary objectives, the study aims to:

• Describe the sociodemographic and clinical characteristics of post bariatric surgery patients.
• Assess changes in quality of life of the post-surgery patients.
• Explain changes of post-surgery in eating behavior and activity varied according to gender
• Explain changes of post-surgery in eating behavior and activity varied according to socio-economic conditions
• Explain changes of post-surgery in eating behavior and activity varied according to inter-generational relation
• Have a overview on the surgery as a turning point in the life of patients
• Estimate the relevant message of cares given to patients, in order to better adjust medical intervention, in conjunction with patients and their family members.

This is a prospective observational study. It will be performed in two university hospitals: CHU Ambroise Paré at Boulogne-Billancourt city and CHU Pitié Salpétrière at Paris, in nutrition department and metabolic surgery department. The study will involve collaboration of a team of social researchers.

Inclusion Criteria:

• Aged ≥ 18 years
• Eligible to undergo bariatric surgery
• Post bariatric surgery follow-up visits will take place in the nutrition department
• Living together with family member (children aged 11-17 years, parents, spouse, cohabitee or partner in civil union)
• Informed consent signed

Exclusion Criteria:

• Higher-order cognitive disorders
• Language difficulties in understanding
• Living alone or living without any family member

Patients who will undergo bariatric surgery (bypass or sleeve) and live together with their families.