Obesity is a worldwide epidemic and is known to increase the risk of cardiovascular disease, type 2 diabetes, and certain forms of cancer. In addition, obesity is now recognized as an important risk factor in the development of several respiratory diseases. Of these respiratory diseases, it has already been well established that obesity can lead to obstructive sleep apnea (OSA) and obesity-hypoventilation syndrome (OHS). More recent data suggest that the prevalence of wheezing and bronchial hyper-responsiveness, two symptoms often associated with asthma, are increased in overweight and obese individual. Indeed, epidemiological studies have reported that obesity is a risk factor for the development of asthma. Furthermore, a number of studies indicate that obesity is also associated with a higher risk of developing deep vein thrombi, pulmonary emboli, pulmonary hypertension, and pneumonia. Finally, weight reduction has been shown to be effective in improving the symptoms and severity of several respiratory diseases, including OSA and asthma. Thus, overweight and obese patients should be encouraged to lose weight to reduce their risk of developing respiratory diseases or improve the course of pre-existing conditions.