It is therefore our hypothesis that a high-leucine essential amino acids mixture specifically designed to stimulate protein anabolism will target the metabolic alterations of COPD patients. In the present study, the acute effects of an EAA nutritional supplement on whole body, muscle and liver protein metabolism will be examined in COPD patients and compared to a supplement consisting of a balanced mixture of total amino acids. The principal endpoints will be the extent of stimulation of whole body protein synthesis as this is the principal mechanism by which either amino acid or protein intake causes muscle anabolism, and the reduction in endogenous protein breakdown. Both endpoints will be assessed by isotope methodology which is thought to be the reference method.