A system for obesity control includes a sheath and a plurality of medical devices. The sheath has a proximal end, a distal end, and a lumen extending therebetween. The medical devices are disposed within the lumen. Each medical device includes a shell defining a cavity, the shell being movable between a deformed state and an unstressed state; a magnet disposed within the cavity; and a filler material disposed within the cavity. The filler material conforms to a shape of the shell when the shell is in the unstressed state. The filler material changes state to maintain a shape of the shell in the deformed state.