Separation as a new animal model for self-induced weight loss.

Animal models for weight loss are generally either stress mediated or following diet restriction (DR) schedules. We investigated weight loss in mice subjected to activity stress (ACT), DR schedules of 40, 60 and 100% of daily requirements, and propose a new model for animal weight loss based upon separation. Mice were separated (SEP) from each other by perspex partitioning for 23 h per day, with free access to food for one hour. No significant differences in weight loss were found between the ACT, SEP and 40% groups. However, mean food intake in the 40% group was half that of the ACT group (p < 0.001) and significantly less (p < 0.01) than the SEP group, which consumed amounts equivalent to 65% of daily requirement. Separation of mice increases metabolic demands and may be used as a new, easily performed, animal model for weight loss.