An ingestible gastrointestinal capsule (GIC) for mechanically stimulating a segment of the gastrointestinal (GI) wall by alternately and repeatedly pressurizing, and/or vibrating it is provided. The GIC is programmed to being activated following a predefined time delay. The activated GIC agitates, shakes, rattles, jolts, vibrates and/or moves in a reciprocal expanding and contracting motion thereby mechanically stimulating the adjacent segment of the GI wall at a targeted location. Activation of the GIC may include a number of automatically accomplished partial activations, such as when the time elapsed from the moment of setting the GIC on equals a predefined time delay; when the mechanical load applied onto the GIC exceeds, and/or gets lower than a respective predefined level of mechanical load; when the ambient pH reaches a predefined level, or changes, and/or a temperature associated with the user reaches a predefined threshold. Agitation is accomplished by means of agitation means embedded in the GIC. Such agitation means includes an unbalanced weight attached to the shaft of an electric motor, an actuator implemented by, such as an electric solenoid, an electro-active polymer (EAP), a dielectric elastomer actuator (DEA), embedded in a GIC of the invention.