A system for allocating energy values to foods. It was developed in the 19th century by the American chemist W. O. Atwater. The system uses a single energy value (factor) for each of the main groups of energy nutrients (protein, fat, and carbohydrate), regardless of the food in which it is found. The energy values (based on the average heats of combustion of each group and corrected for losses in digestion, absorption, and urinary excretion of urea) are 17 kJ/g (4.0 kcal/g) for protein, 37 kJ/g (9.0 kcal/g) for fat and 17 kJ/g (4.0 kcal/g) for carbohydrates. The system also includes a rounded energy value for alcohol of 29 kJ/g (7.0 kcal/g). Partly because of its simplicity, the Atwater general factor system is still widely used today to estimate the net metabolizable energy of typically consumed foods.
Subjects: Sports and Exercise Medicine.