Oxygen consumption and locomotor activity during restricted feeding and realimentation.

Both the resting rate of O2 consumption and the heat increment in response to an intubated meal were measured in male rats following periods of food restriction and during realimentation. In one experiment, resting rates of O2 consumption were significantly reduced below control values after food consumption had been restricted and during a substantial part of an 11-day period of controlled realimentation. In a second experiment, the heat increment in response to an intubated meal was also significantly less following an interval of food restriction and during the early stages of realimentation. The reduction in O2 consumption was not related to reduced locomotor activity. These results obtained whether O2 consumption was measured in absolute amount or was referenced to an estimate of the animal's metabolically active tissue (kg body wt0.75). It is suggested that these metabolic adaptations contribute significantly to the enhanced efficiency of food utilization reported in food-restricted animals during controlled realimentation.