A gastric belt has a wall of a chamber (3) forming a working face (5) with a length (l5) in the flat position of the belt. The length (l5) is equal to or greater than a length (l4) of the wall of the chamber (3), which forms the back side (4) in such a way that when the belt is fastened in the form of a circle and is inflated, the chamber wall forms folds.
