Weight loss commonly occurs in patients with chronic obstructive pulmonary disease (COPD), negatively influencing their quality of life, treatment response and survival. Loss of muscle protein is generally a central component of weight loss in COPD patients. Attempts to reverse muscle loss in COPD by supplying large amounts of protein or calories to these patients have been unsuccessful. Gains in muscle mass are difficult to achieve in COPD unless specific metabolic abnormalities are targeted. The investigators recently observed that alterations in protein metabolism are present in normal weight COPD patients. Elevated levels of protein synthesis and breakdown rates were found in this COPD group indicating that alterations are already present before muscle wasting occurs. Furthermore, reduced plasma essential amino acid (EAA) levels were observed in COPD patients. These reduced EAA plasma levels were significantly related with the presence of muscle wasting in COPD. Until now, limited research has been done examining protein metabolism and the response to feeding in patients with COPD. Previous studies support the concept of essential amino acids (EAA) as an anabolic stimulus in the young and elderly and in insulin resistant states. Until yet no information is present on the anabolic effects of EAA in elderly COPD patients.