Basal metabolic rate (BMR) is the minimal rate of energy expenditure per unit time by endothermic animals at rest. (McNab, B. K. 1997). On the Utility of Uniformity in the Definition of Basal Rate of Metabolism.Physiol.Zool.Vol.70; Metabolism refers to the processes that the body needs to function.asal metabolic rate (BMR) is the minimal rate of energy expenditure per unit time by endothermic animals at rest. (McNab, B. K. 1997). On the Utility of Uniformity in the Definition of Basal Rate of Metabolism. Physiol. Zool. Vol.70; Metabolism refers to the processes that the body needs to function.