Long-term moderate caloric restriction and social isolation synergize to induce anorexia-like behavior in rats.

Abstract Moderate caloric restriction is an effective strategy to delay the onset of chronic disease states. Conversely, social isolation carries an increased risk of morbidity and mortality from several causes. The present studies were designed to investigate the long-term effect of the two combined exposures. Two-month old male rats of the Fischer 344 strain were fed either ad libitum or under a regimen of caloric restriction and each of the two animal sets were housed either in group or in isolation. Food consumption and animal growth curves were as expected during the first 6 weeks of observation. However, starting at two months and continuing until the fifth month of-follow-up, rats exposed to both caloric restriction and social isolation showed signs of altered feeding behavior, in that they were unable to complete their (already restricted) meal. Furthermore, this was accompanied by a corresponding decrease in growth rate, until no further increase in body weight was observed. Restoration of group-housing conditions led to a reversal of this phenotype. We conclude that chronic moderate caloric restriction and social isolation synergize to induce anorexia-like behavior, representing a simple and reproducible model to study such an eating disorder.