Why doesn the sum of the % calories from protein, fat, carbohydrate, and alcohol equal 100%?
Calorie content of individual foods in the NCC Food and Nutrient Database is based mostly on USDA values that have been calculated using the specific Atwater energy factors. These factors are specific to individual foods or groups of foods and take into account energy losses that occur during digestion and metabolism. Therefore, the factors used to determine the caloric content of a food may be somewhat different than the general Atwater factors (4 kcal/g protein, 4 kcal/g carbohydrate, 9 kcal/g fat, and 7 kcal/g alcohol). In calculating the percent of calorie intake from each of the energy nutrients in a daily diet, the NDSR program used the general Atwater factors. The use of the two sets of calorie factors may cause the percent of calories per day from each of the energy nutrients to total more or less than 100%. The following example illustrates the calculation used for the percent of calories from each nutrient and provides examples of specific Atwater energy factors for some food
