Calorie and protein intake and balance of men and women consuming self-selected diets

The calorie and protein intakes of 16 women and 13 men consuming self-selected diets over a 1-yr period were determined. During four 7-day balance periods, corresponding to the four seasons of the year, duplicates of diets consumed and urine and feces excreted were collected for analysis and calculations of available energy and nitrogen balance. During the four balance periods, the food intakes and thus the calorie and protein intake of the subjects decreased as documented by 7-day food records immediately before and after the balance periods. This unexpected decrease in food consumption made the nitrogen (N) balance results difficult to interpret. The energy digestibility of these diets ranged from 87 to 98% (mean +/- SD, 93.7 +/- 2.3). The nitrogen digestibility of the diets ranged from 80 to 96% (mean +/- SD, 88.6 +/- 3.4). The analyzed calorie values (heats of combustion) of the diet composites were approximately the same as calorie values of these diets calculated from diet records using food tables. This is surprising since calorie values in food tables are available energies which have been corrected by a coefficient of availability.