We previously reported that carbonated water ingestion induced fullness and gastric motility. In order to determine whether such satiating effects occur through oral carbonic stimulation alone, we conducted modified sham-feeding (SF) tests (carbonated water ingestion (CW), water ingestion (W), carbonated water sham-feeding (CW-SF), and water sham-feeding (W-SF)), employing an equivalent volume and standardized temperature of carbonated and plain water, in a randomized crossover design. Thirteen young women began fasting at 10 p.m. on the previous night and were loaded with each sample (15ºC, 250 mL) at 9 a.m. on separate days. Electrogastrography (EGG) recordings were obtained from 20 min before to 45 min after the loading to determine the power and frequency of the gastric myoelectrical activity. Appetite was assessed using visual analog scales. After ingestion, significantly increased fullness and decreased hunger ratings were observed in the CW group. After the load, transiently but significantly increased fullness as well as decreased hunger ratings were observed in the CW-SF group. The powers of normogastria (2-4 cpm) and tachygastria (4-9 cpm) showed significant increases in the CW and W groups, but not in the CW-SF and W-SF groups. The peak frequency of normogastria tended to shift toward a higher band in the CW group, whereas it shifted toward a lower band in the CW-SF group, indicating a different EGG rhythm. Our results suggest that CO2-induced oral stimulation is solely responsible for the feeling of satiety. Moreover, different gastric-contraction rhythms (slow or fast) were induced by oral carbonic stimulation alone and carbonated water ingestion.
Keywords: appetite; carbonated water; electrogastrography; oral stimulation; sham-feeding.