Body composition, resting and running metabolic rates, and net cost of running in rats during starvation

Resting metabolic rate decreases during starvation. However, effects of starvation on the cost of running are not clear. The aim of this study was to examine the effects of 5 days starvation on body composition, resting metabolic rates, running metabolic rates, and net cost of running in male rats. Five days starvation resulted in reductions of 70% fat, 8% protein and 12% carbohydrates. Mass(-0.75) specific resting metabolic rate was significantly reduced from 3.69 +/- 0.27 to 2.73 +/- 0.17 W kg(-0.75) after 5 days starvation. The reduction in metabolic rate after 5 days starvation was maintained during running, in that running metabolic rate was reduced from 10.65 +/- 0.41 to 8.97 +/- 0.47 W kg(-0.75). The net costs of running were calculated and expressed as the costs of moving 1 kg a distance of 1 m. After 5 days of starvation it was reduced from 31.16 +/- 2.03-29.79 +/- 1.69 J m(-1) kg(-1). The reduction however was not significant. The present results therefore suggest that 5 days starvation resulted in a metabolic depression of the resting metabolic rate that was maintained during running. However, the net cost of running remained unchanged, suggesting that the muscle tissues are not significantly involved in the metabolic changes during starvation.