Calculation and determination of metabolizable energy in mixed diets to humans

Several approaches are currently in use for calculating metabolizable energy of mixed diets from the foods and nutrients they contain. This study compares the metabolizable energy content of six low fiber and one high fiber diet as calculated by conventional procedures (ie, using Atwater's general factors, Merrill and Watts specific factors, and the British procedure where the monosaccharide equivalent of available carbohydrates is multiplied by 3.75 kcal/g) with values for metabolizable energy measured in balance experiments on human subjects. For the low fiber diets, the conventional procedures for calculation of metabolizable energy showed an average deviation between calculated and measured values of up to about 6% of the value obtained in balance experiments. For the high fiber diet Merrill and Watts specific factors and Atwater's general factors were superior to the British approach for calculation of metabolizable energy. Fecal energy content in relation to intake of undigestible energy is discussed.