1. A system for stimulating incretin-producing cells (IP-cells) in an intestinal tract of a patient to secrete an incretin, the system comprising:
a device configured to travel through the intestinal tract and electrically stimulate the IP-cells at any location in the intestinal tract; and
a controller for delivering an electrical signal from the device to an intestinal wall proximate the device, wherein the electrical signal includes a waveform configured to electrically stimulate the IP-cells in the intestinal tract to secrete the incretin without causing a peristaltic contraction.