Abstract: An expandable intragastric balloon implantable in the stomach for the treatment of obesity, comprising an outer casing (2) which is sufficiently flexible to change from a reduced volume configuration to an expanded configuration, thereby imparting the balloon (1) with its functional shape. The balloon further comprises means (3) for forming the outer casing (2), which are structurally integrated into the balloon (1), but generally are separate from the outer casing (2). Once the balloon (1) has been implanted, the aforementioned forming means (3) can be actuated in order to: (i) exert a sufficient driving pressure on the outer casing (2) such as to force the deployment thereof, and (ii) occupy a sufficient volume inside the outer casing (2) in order to produce the deployment of the outer casing (2) from the reduced volume configuration to the expanded configuration thereof.