Sexually dimorphic effects of forced exercise on food intake and body weight in the rat

The food intake (FI), body weight (BWt) and water intake (WI) of adult male and female rats were compared during a seven day period of forced exercise in a treadmill. Work loads for the exercised groups were gradually increased across the seven-day test period, whereas work loads for the sedentary controls were maintained at the same level used during a previous three-day training period. Relative to their respective control groups, male rats showed a decrease in FI and BWt in response to the exercise challenge, but female rats showed an increase in FI sufficient to maintain their BWt at control levels. Both male and female rats showed a reliable increase in WI during the period of forced exercise. These sexually dimorphic changes in FI and BWt in response to forced exercise indicate that female rats are capable of demonstrating a more vigorous defense of BWt than are male rats and suggest that there is a sex difference in the long-term control of feeding behavior in the rat.