In Chinese medicine, anytime you insert a needle, there will be a change in the body, no matter if the point is a "real" point or not. Our energy field isn't limited to these little points on our bodies, those are simply the best access points to our energy.
So the next time you see a study with results that "are only slightly better than sham acupuncture," please read it with a grain of salt. Sham acupuncture is not a true control, and should not be confused for one, when writing the conclusions for a study.