Chronic obstructive pulmonary disease (COPD) is one of the major diseases worldwide. Nutritional depletion is a common problem in COPD patients and also an independant predictor of survival in these patients. Many data are helpful for determining nutritional depletion, including anthropometric measurement, laboratory markers, body composition analysis (fat-free mass and lean mass), and body weight. The mechanism of nutritional depletion in patients with COPD is still uncertain. It may be associated with energy/metabolism imbalance, tissue hypoxia, systemic inflammation, and leptin/orexin disorders. In patients with nutritional depletion, growth hormone and testosterone can be used for nutritional therapy in addition to nutrition supplementation.