THE IMPORTANCE OF TASTE AND PALATABILITY IN CARBOHYDRATE-INDUCED OVEREATING IN RATS

Rats offered a carbohydrate solution (sugar or polysaccharide) in addi tion to chow typically overeat and gain excessive weight. The present study sought to determine if the palatable taste of these solutions co ntributes to the overeating response. Adult female rats were fitted wi th chronic intragastric catheters and given ad libitum access to chow and a drinking fluid that was paired with intragastric infusions. For one group (P+S), the flavored solution was a highly preferred mixture of 2% Polycose and 0.2% saccharin paired with intragastric infusions o f 30% Polycose. For a second group (SOA), the flavored solution (0.03% sucrose octaacetate) had unpreferred bitter taste and was paired with intragastric infusions of 32% Polycose. Thus both groups were effecti vely exposed to the postingestive effects of 32% Polycose but paired w ith a palatable (P+S) or unpalatable (SOA) flavor. A control group had water to drink paired with intragastric water infusions. During the 4 -wk experimental period, the P+S group consumed 34% more total energy (chow + Polycose) and gained more weight than did the SOA and control groups. The P+S group also consumed substantially more flavored soluti on and more energy as Polycose compared with the SOA group. The SOA gr oup did not gain reliably more weight than the control group, although their total energy intake was 13% higher than that of the controls. I n a choice test conducted at the end of the experiment, the P+S group displayed a strong preference (98%) for the Polycose + saccharin solut ion over water. In contrast to the control group, which avoided the SO A solution relative to water, the SOA group preferred the SOA solution (71%) confirming prior reports of Polycose-conditioned SOA preference s. These results demonstrate that palatability has a major effect on t he overeating and obesity produced by carbohydrate solutions. In the a bsence of a highly preferred taste, the postingestive actions of Polyc ose produce only a small hyperphagic effect and no excess weight gain.