Tumor growth in rats: conditioned suppression of food intake and preference.

Rats with experimental tumors developed strong aversions to a novel diet they consumed during tumor growth. Aversions were not evident when the food available during tumor growth was familiar laboratory chow. The impact of learned food aversions on tumor anorexia was evidenced by more severe and long-lasting hypophagia in tumor-bearing animals maintained on a novel diet than in those maintained on laboratory chow. Thus, when a diet is a salient target for the development of learned aversions, the aversions that develop to it can make substantial contributions to the overall syndrome of tumor anorexia. In addition, frequent changes of the diet offered to tumor-bearing rats was associated with milder anorexia than that produced by maintaining tumor-bearing rats on a constant diet. Apparently, the prevention of learned food aversions, or the repeated replacement of aversive foods, can minimize the impact of learned food aversions and attenuate anorexia in tumor-bearing animals.