the atwater general factor for dietary carbohydrate is
Atwater system Based on the work of Atwater, it became common practice to calculate energy content of foods using 4 kcal/g for carbohydrates and proteins and 9 kcal/g for lipids.[2] The system was later improved by Annabel Merrill and Bernice Watt of the USDA, who derived a system whereby specific calorie conversion factors for different foods were proposed.[3] This takes cognizance of the fact that first the gross energy values of the protein, fats and carbohydrates from different food sources are different, and second, that the apparent digestibility of the components of different foods is different.