A calculated measurement of the difference in the amount of food (material, usually of plant or animal origin, that contains essential nutrients such as carbohydrates, fats, proteins, vitamins, and/or minerals and that is ingested and assimilated by an organism to produce energy, stimulate growth, and maintain life) taken in for utilization by the body between two points in time or two conditions, expressed as the result of the subtraction in and of itself without comparison by ratio with another quantity.