Explain the Obligatory Losses of Nutrients?

Obligatory losses of nutrient are defined as 'the losses that occur when an individual is put on a diet free of that nutrient'. For example, when we are on a protein free diet, we continue to lose protein in the form of urinary urea and other nitrogenous compounds. Within 5 to 6 days on a protein free diet, the total nitrogen losses as urea and other compounds stabilize to a low and constant value. The amount of dietary protein needed to replace these losses has been experimentally determined. These represent the maintenance requirement for protein in an adult. This method, however, has been discarded as it represents a non-physiological state.