Energy: Intake and Expenditure
The term ‘energy’ is confused or poorly understood because in lay language it is often used to refer to a subjective feeling of alertness. In nutritional science, ‘energy’ refers to the metabolic fuel needed for all bodily functions. We need a continuous supply of energy for the basic physiological functioning of the body, particularly at cellular level in active transport pumps, but also more apparent functions, such as breathing, digestion and excretion. The most energy-demanding organ is the brain. In addition, our muscles require energy to function, the heart to keep blood circulating to the tissues and our skeletal muscles to maintain posture, balance and mobility. For any activity, whether it has to do with our occupation, movement, domestic activity or leisure, more energy must be supplied. Even when we are asleep, we are using energy. In the early years of life and during pregnancy and lactation, additional energy is required for growth.