There is a common clinical impression that because the nitrogen excretion after injury roughly parallels the increased resting metabolic expenditure and weight loss, the primary source of extra fuel is derived from protein. This study has been undertaken to evaluate the caloric contribution of protein to the daily resting metabolic expenditure (RME). 2. Under the most extreme circumstances of nitrogen excretion, massive soft tissue injury, the caloric contribution of protein is only 20 percent of the RME. Body fat stores are the only other major source of fuel from which the semistarved patient can meet the increased demands for energy. 3. Any form of severe injury impairs the mechanisms by which protein breakdown and nitrogen excretion are reduced. 4. Patients undergoing elective operation in this study did not have a significant rise in RME or nitrogen excretion.
