[Etiological and exacerbation factors for COPD. Body weight loss]

Hunger or malnutrition is not only a historical issue but also a current problem worldwide. Biological responses to hunger are evolutionary prepared in our body, including energy generation by degradation of body proteins. Extreme weight loss (malnutrition) can cause air space enlargement in human and rodents. However, the changes in rodents could be reversible, since refeeding could repair the pathology. On the other hand, weight loss is a common feature in patients with more severe COPD. Complex factors, such as increased energy consumption, decreased food uptake by low grade inflammation, socio-economic factors and so on, are involved in weight loss. Weight loss in patients with COPD also increases the risk of exacerbation, hospitalization, and death.