Gender dimorphic effects of voluntary running in laboratory rats depends on maturational status.

This study examined the effect of 24 hr per day wheel access on running, body weight, and food intake for 30- or 50-day-old male and female rats under ad lib feeding conditions. Food intake and body weight were also monitored in a control group housed without access to running wheels. A dimorphic effect was observed after wheel introduction in 50-day-old but not 30-day-old rats: A temporary decline in food intake and a lasting decrease in body weight occurred for active male rats in comparison to their sedentary controls, and wheel access facilitated food intake and preserved body weight gain in female rats in comparison to their sedentary counterparts. Hyperphagia in adult females is interpreted in terms of the evolutionary acquired advantage linked to their reproductive function.