In the preceding sections of the unit, you studied how the products of digestion of food, viz: amino acids, sugars and fatty acids are absorbed and transported to the body tissues. The oxidation of these compounds yields virtually all the chemical energy required animals and the use of this chemical energy is referred to as their energy metabolism.
Generally carbohydrates and fats are the fuel which provides energy but other organic compounds are within wide limits interchangeable in energy metabolism. How do we measure the rate of metabolism or the actual amount of energy liberated during oxidative metabolism? One way could be to measure the total heat produced by the organism per unit of time. This is the metabolic rate of the organism. The metabolic rate can be determined by using the formulation:
Rate of energy intake - rate of energy loss per unit time = metabolic rate