Food flavor preferences produced by drinking glucose and oil in normal and diabetic rats: evidence for conditioning based on fuel oxidation.

Free-feeding normal and streptozotocin-diabetic rats were allowed to drink 10 ml of 35% glucose solution or an equicaloric 15% corn oil emulsion during the 1st hr of the dark period. While the drinks were available, the rats ate food that contained distinctive flavors such that a particular flavor was always associated with a particular drink. It was found that relative to a control flavored food given without a nutritive drink, (1) flavored food consumed with a glucose solution was preferred by normal rats but avoided by diabetic rats, and (2) flavored food consumed with an oil emulsion was preferred by both normal and diabetic rats. When given a choice between one flavored food paired with drinking glucose and another flavored food paired with drinking oil, normal rats showed no preference but diabetic rats preferred the oil-paired flavored food. These results can best be explained by consideration of the different ability of normal and diabetic rats to oxidize glucose.