This project is based on a clinical protocol performed in massively obese subjects (BMI>40 kg/m²). The investigators plan to recruit 70 obese patients addressed for gastric banding and 70 candidates for gastric bypass. Clinical phenotype, biochemical analysis, body composition, systemic and adipose tissue inflammation, endotoxemia and gut microbiota will be assessed at baseline and 1, 3 and 12 months after surgery. Specific food consumption will be recorded at every time point. A group of 40 lean healthy volunteers will undergo the same phenotyping.