In the last few decades, obesity has captured the attention of the medical community, as well as the general public. Obesity has been shown to be a direct cause or a contributor to the development of various chronic diseases. In contrast, higher weight has been linked to better outcomes in patients with chronic obstructive pulmonary disease (COPD). It also has been recognized that “not all weight has been created equal” and its not the absolute weight in kilograms or the body-mass index (BMI), but rather the fat-free mass index (FFMI) that is a better measure of the nutritional status and the overall prognosis in COPD patients. While the impact of the weight and the nutritional status on the lung cancer outcomes has been similar to that of COPD, the relationship between the obesity and asthma has been more complex and multi-faceted. The article will offer a concise, rather than a comprehensive review of such relationships between the nutritional status and the natural history of three chronic lung diseases. The effects of nutritional supplements, alternative medications, and other interventions will be discussed in the context of the individual diseases (COPD, asthma and lung cancer).