Beneficial effects of exercise on growth of rats during intermittent fasting.

An 8-wk trial was conducted to compare the effects of exercise and intermittent fasting, either singly or combined, on growth responses of rats. Four-week-old male Wistar rats, 85-110 g each, were assigned to one of four groups (n = 9): control, exercise on a motor-driven treadmill, fasting every other day (EOD) and fasting EOD and exercise combined. At the end of the trial, the exercised rats had consumed 7% less feed, had gained 7% less weight and had 36% less carcass fat than the control rats. Fasting on alternate days markedly reduced the growth rate of the young rats. Fasted-EOD rats weighed less than half as much as the control rats, had 64% less carcass fat and 51% less lean mass and had smaller livers, kidneys, hearts, tibias and tibialis anterior muscles. The addition of exercise to the fasting EOD regimen improved the growth of the animals. When the fasted-EOD rats were also exercised, they gained 29% more weight, consumed 11% more feed and had carcasses that contained 29% more lean mass and 18% less fat than the fasted-EOD rats. The data suggest that exercise may be beneficial where feed restriction is episodic, allowing some capacity for catch-up growth.