Drinking saccharin increases food intake and preference—IV. Cephalic phase and metabolic factors

Abstract

Rats that drink saccharin solution increase their short-term food intake and develop a preference for flavored food eaten when saccharin is ingested. In this paper, we examined whether these effects are mediated by cephalic-phase metabolic reflexes. The results show that the cephalic-phase insulin response could be dissociated from food intake in three ways. (1) Drinking saccharin increased the food intake and food preference of rats with sham surgery (SHM) or celiac vagotomy (CV), but not hepatic vagotomy (HV); it produced a short-lived increase in plasma insulin levels in all three groups, but the insulin response of both the CV and HV group was attenuated relative to the SHM group. (2) Rats increased food intake even when a 90 min interval was imposed between drinking saccharin and eating food, although insulin and glucose levels returned to normal within 30 min of drinking saccharin. (3) Streptozotocin-induced diabetes did not affect the increased feeding response to saccharin. The failure of rats given hepatic vagotomy to increase food intake and food preference when drinking saccharin suggests that a hepatic mechanism is involved. We propose that drinking saccharin increases food intake by temporarily altering the disposition of metabolic fuels towards storage and away from oxidation. Flavored food eaten after drinking saccharin becomes preferred because it provides fuel to counteract this reduction in oxidation.