Did you know that the resting or basal metabolic rate, the amount of energy in relation to body weight required to sustain such basic functions as the heartbeat, breathing and the maintenance of body heat decreases after infancy? A newborn baby needs about twice the energy of an adult because it is growing and the proportion of such metabolically active tissues as the liver, brain and skeletal muscle is increasing. Energy requirement falls rapidly until adolescence when it is only slightly higher than in adults of the same weight. Adult resting metabolic rate then declines every decade as people become less active.