Palatability and foraging cost interact to control caloric intake

The combined effects of meal cost and food flavor on meal size were studied with a method that avoided the covariation of nutrient composition and cal oric density with palatability. As rats (Rattus norvegicus) drank flavored fluids (unpalatable 0.05% sucrose octaacetate [SOA], neutral 0.05% sacchari n, and palatable 2% Polycose + 0.2% saccharin [P + S]), liquid diet was inf used intragastrically. Relative to saccharin, rats with free access ate 10% more calories in larger meals while consuming P + S and initially ate fewe r calories in smaller but more frequent meals while drinking SOA. Other rat s lever-pressed to begin meals, which halved meal number and doubled meal s ize relative to the free-access group. Although foraging rats also ate larg er P + S meals and smaller SOA meals, the changes did not affect total inta ke. Without the usual differential postingestive effects of foods that diff er in palatability, making food more costly blunts rats' response to its fl avor.