Methods, devices, tools, instruments and systems for treating a patient to induce weight loss. In one method embodiment, a device, including an expandable member in a collapsed configuration, is passed through an opening in the skin of the patient, and into the abdominal cavity of the patient. At least a portion of the expandable member is anchored relative to at least one structure in the abdominal cavity, without piercing the stomach. The expandable member is expanded to an expanded configuration in a space in the abdominal cavity to perform at least one of: prevention of expansion of the stomach of the patient into the space; and compression of a portion of the stomach.