Metabolizable energy of diets low or high in dietary fiber from fruits and vegetables when consumed by humans.

The metabolizable energy (ME) of two diets, which differed in their content of dietary fiber mainly from fruits and vegetables, was determined in balance experiments in eight young women. The ME of the diets was also calculated by the specific factors of Merrill and Watt, by the general factors of Atwater, by the modification of Atwater's procedure used in the Federal Republic of Germany, and also by the equations of Southgate, of Miller and Payne, and of Miller and Judd. The daily intake of fruits, vegetables and potatoes was 505 and 1235 g with the low and the high fiber diets, respectively. Normally, young German women consume only 350 g of these foods each day. Dietary fiber intake was 18.8 g/d with the low fiber diet and 52.0 g/d with the high fiber diet. Daily gross energy intakes were 8540 and 8916 kJ (2041 and 2131 kcal) with the low and the high fiber diets, respectively. The apparent digestibility of energy was lower when the high fiber diet was consumed. Measured ME was 7665 and 7544 kJ/d (1831 and 1802 kcal/d) with the low and high fiber diets, respectively. It was calculated that fiber from fruits and vegetables contributed to ME about 3 kJ (0.7 kcal) per gram of fiber. On the average, the ME of the low fiber diet could be predicted by all calculation procedures except the formula of Miller and Judd. The ME of the high fiber diet could best be predicted by the specific factors of Merrill and Watt and by the Southgate formula.