The interest in nutrition in the management of chronic obstructive pulmonary disease (COPD) has increased dramatically during the past two decades. Traditionally, weight loss was considered to be an inevitable and irreversible component of the terminal progression of the disease process. From this viewpoint, it could be argued that nutritional support might actually influence the disease adversely by inducing additional metabolic and ventilatory stress on the respiratory system. Studies demonstrating the disturbed energy balance during weight loss in COPD have, however, challenged this approach. Furthermore, studies taking a more holistic view of COPD, recognizing the irreversible respiratory impairment and the systemic consequences of the disease, revealed that nutritional depletion contributes to respiratory and peripheral skeletal muscle weakness and to decreased exercise performance, independent of impaired lung function. In some patients, this condition is reversible after protein-energy supplementation. Moreover, recent studies have shown that nutritional abnormalities in patients with COPD relate to a disturbed energy balance and to altered regulation of substrate metabolism caused by changes in anabolic and catabolic stimuli. Further characterization and unraveling of these pathophysiologic abnormalities may enlarge the perspective for nutritional intervention, not merely by protein-energy supplementation to reverse weight loss, but also by targeted metabolic modulation of specific problems in subgroups of COPD patients, through nutritive and non-nutritive actions at either physiologic or pharmacologic doses.