Exploring body weight, voluntary activity, and intrinsic value in rats.

Modeling activity-based anorexia, food-deprived rats consistently show that activity increases as weight decreases. This effect was explored in 8 food-deprived, Sprague-Dawley rats as potentially mediated by intrinsic value of activity. Running-wheel activity rates were recorded for free-fed weight, reduction to 90% of free-fed weight, and to 80% of free-fed weight.