Relationship of body energy status to inflammation-induced anorexia and weight loss

The response to acute inflammation of rats at two levels of prior weight reduction were compared with normal-weight rats to examine how prior alterations in body energy status influence inflammation-induced anorexia and weight loss. Specifically, body weights were either reduced by 6%, the level of weight loss expected in normal-weight rats following induction of acute inflammation, or by 12%, a level 6% below that expected of the normal-weight rats. Rats were either allowed to eat ad lib. on postinflammation Day 1 or were kept on food restriction until Day 5, when anorexia was no longer expected to be present. As predicted, normal-weight rats allowed to eat ad lib. beginning Day 1 displayed the most severe anorexia. Total food intake of this group over the first 5 days following inflammation induction was 33% less than the control (CON) group. Rats with 6% prior weight reduction displayed a milder anorexia, eating only 15% less than the CON group over the first 5 days. In contrast, rats with 12% prior weight reduction ate the same amount of food as the CON group. Interestingly, similar feeding patterns were observed in rats that resumed ad lib. feeding on Day 5. The outcome of these various feeding patterns was to bring body weights of all the inflammation groups to the same level, approximately 6% below CON group weights. These results provide further evidence that proinflammatory mediators induce a temporary reduction in the amount of body tissue (weight) spontaneously maintained that is directly proportionate to the magnitude of insult.