ABSTRACT
Energy is well recognized as a prime requirement for humans and other living organisms. The major dietary sources of energy-yielding substrates are carbohydrates, fats, and proteins.1 After these food components are digested and the resulting nutrients are absorbed, they are converted, in part, to chemical energy in the form of adenosine triphosphate (ATP) and other high-energy compounds; ATP is the central chemical intermediate involved in many processes that require energy. Parts of the nutrients also are used, of course, for the growth and maintenance of body tissues. It is a common knowledge that if the food energy intake is inadequate to meet the body’s energy requirements, loss of body weight occurs, body carbohydrate and fat stores are gradually decreased, and, because of the urgent drive for energy, the body protein itself is metabolized to supply energy. Severe emaciation and drastic metabolic alterations (e.g., acidosis, ketosis, loss of cations and nitrogen, dehydration) ensue and, if extended, may result in death.
