Devices, systems and methods are disclosed for treating or preventing gastroparesis, functional dyspepsia, and other functional gastrointestinal disorders. The methods comprise transmitting impulses of energy non-invasively to selected nerve fibers, particularly those in a vagus nerve. The methods provide damaged interstitial cells of Cajal (ICC) with trophic factors via vagal afferent nerve fibers, thereby reversing ICC damage, and as a consequence improving gastric motility. The methods also increase levels of inhibitory neurotransmitters in the brain so as to decrease neural activity within the area postrema, or they deactivate a resting state neural network containing parts of the anterior insula and anterior cingulate cortex, which will thereby reduce abnormal interoception and visceral hypersensitivity.