Energy metabolism and growth in rats adapted to intermittent starvation

Abstract

Food intake, weight gain and femur length were measured in each of 2 experiments for 3 groups of male albino rats. One group was intermittently fasted (for periods of 1-3 days) and given free access to food (for 1 day), 1 group was given daily a restricted food ration, and the third was fed to appetite. In addition, total O2 consumption of a group of female intermittently starved rats and of a group of well-nourished controls was measured for 24 hours. In a pair-feeding experiment lasting 11 weeks the loss of weight and the length of femur were equal in the groups subjected to either intermittent or continuous underfeeding; the food intake was reduced to 46% of that of the controls. In a pair-gaining experiment the intermittently starving rats consumed the same amount of food as the continuously underfed group. Assessment of the total O2 consumption during 24 hours revealed that the rats intermittently starved for 8 weeks had, as compared with non-fasted controls, a higher oxygen consumption/unit of surface area, during the period of relative rest, i.e. in daytime, whereas during the period of maximum physical activity (at night) the consumption was substantially reduced. Mean values for O2 consumption for the whole 24 hour period were significantly lower for intermittently starving animals than for controls. From the results it appears that rats adapted to intermittent starvation compensate by a reduced energy output during the period of maximum physical activity for the increase in tissue oxidation activity, which manifests itself also by a higher resting and basal metabolism.