Metabolizable energy in humans in two diets containing different sources of dietary fiber. Calculations and analysis.

The metabolizable energy (ME) of two high fiber diets, providing between 33 and 74 g dietary fiber (DF) per day, was calculated by application of Atwater's general factors (4, 9 and 4 kcal/g protein, fat and carbohydrate, respectively), Merrill and Watt's specific factors, and the British approach in which ME from carbohydrates is calculated by multiplication of the monosaccharide equivalent by 3.75 kcal/g. These factors were applied to the intakes of fat, protein and carbohydrate of 20 human subjects in two balance experiments. ME estimated by Merrill and Watt's factors agreed better with ME estimated in the balance experiment than did ME calculated by Atwater's factors or by the British approach. It was calculated that the DF in diet A, derived mainly from cereals, contributed 2.5 +/- 1.4 kcal/g to ME of the diet. The corresponding figure for DF in diet B, derived mainly from beans, vegetables and fruits, was 3.1 +/- 1.2 kcal/g. It was concluded that Merrill & Watt's factors represent the best system in current use for calculation of ME in DF-rich diets.