An inflatable and adjustable gastric band to be positioned around a segment of the digestive tract in order to narrow the latter, said gastric band comprising: ▪ a hollow flexible band, which is resilient and comprises an inner wall and an outer wall defining an inflatable leaktight chamber with an inflation opening; ▪ a flexible inflation tube whose distal end (6 d) is connected to the inflation opening of the band, and whose proximal end (7 p) is intended to be connected to inflation means; ▪ the tube and the band being provided, in the respective distal end areas and thereof, with complementary closure means and that are able to mutually engage so as to lock a ring in a closed position, said ring being formed by bringing the distal end (9 d) and the proximal end (13 p) of the band together according to the principle of a slip knot, in particular around the segment of the digestive tract to be narrowed; the closure means of the tube being at least one notch and the closure means of the band being at least one loop, preferably two loops, such that the proximal end (7 p) of the tube is intended to be engaged through said at least one loop of the band as far as a locked closure position once said at least one notch is brought beyond said at least one loop; characterized in that - the hollow flexible band, when not in use and when the tube and the band are not engaged in each other to form the ring, has a preformed curved part which extends starting from the proximal end area thereof and which is continued via a substantially rectilinear part to the free distal end (9 d) of the band, said substantially rectilinear part having a length between 10 and 40%, more preferably between 17 and 35%, even more preferably between 21 ad 33% of a total length of the hollow flexible band so as to facilitate the engagement of the proximal end (7 p) of the tube through said at least one loop of the band, and - said at least one loop being arranged on the outer wall of the substantially rectilinear part of the hollow flexible band. ▪ a hollow flexible band, which is resilient and comprises an inner wall and an outer wall defining an inflatable leaktight chamber with an inflation opening; ▪ a flexible inflation tube whose distal end (6 d) is connected to the inflation opening of the band, and whose proximal end (7 p) is intended to be connected to inflation means; ▪ the tube and the band being provided, in the respective distal end areas and thereof, with complementary closure means and that are able to mutually engage so as to lock a ring in a closed position, said ring being formed by bringing the distal end (9 d) and the proximal end (13 p) of the band together according to the principle of a slip knot, in particular around the segment of the digestive tract to be narrowed; the closure means of the tube being at least one notch and the closure means of the band being at least one loop, preferably two loops, such that the proximal end (7 p) of the tube is intended to be engaged through said at least one loop of the band as far as a locked closure position once said at least one notch is brought beyond said at least one loop; - the hollow flexible band, when not in use and when the tube and the band are not engaged in each other to form the ring, has a preformed curved part which extends starting from the proximal end area thereof and which is continued via a substantially rectilinear part to the free distal end (9 d) of the band, said substantially rectilinear part having a length between 10 and 40%, more preferably between 17 and 35%, even more preferably between 21 ad 33% of a total length of the hollow flexible band so as to facilitate the engagement of the proximal end (7 p) of the tube through said at least one loop of the band, and - said at least one loop being arranged on the outer wall of the substantially rectilinear part of the hollow flexible band.