Method for treating obesity in a mammal which has an oesophagus connected to a stomach at the level of an oesophagogastric junction region, the oesophagogastric junction region exhibiting a zigzag oesophagogastric mucosal junction line and a transverse mucosal fold raised by sling fibres, the mucosal fold being located downstream of the Z line, the mucosal fold and the Z line defining a conical structure delimiting an opening to the stomach, including creating a first stricture zone by reducing the cross section of the opening by introducing at least a first biocompatible substance implanted on or in the wall of the conical structure, at least at the level of the mucosal fold.