Obesity: systemic and pulmonary complications, biochemical abnormalities, and impairment of lung function.

Obesity is currently one of the major epidemics of this millennium and affects individuals throughout the world. It causes multiple systemic complications, some of which result in severe impairment of organs and tissues. These complications involve mechanical changes caused by the accumulation of adipose tissue and the numerous cytokines produced by adipocytes. Obesity also significantly interferes with respiratory function by decreasing lung volume, particularly the expiratory reserve volume and functional residual capacity. Because of the ineffectiveness of the respiratory muscles, strength and resistance may be reduced. All these factors lead to inspiratory overload, which increases respiratory effort, oxygen consumption, and respiratory energy expenditure. It is noteworthy that patterns of body fat distribution significantly influence the function of the respiratory system, likely via the direct mechanical effect of fat accumulation in the chest and abdominal regions. Weight loss caused by various types of treatment, including low-calorie diet, intragastric balloon, and bariatric surgery, significantly improves lung function and metabolic syndrome and reduces body mass index. Despite advances in the knowledge of pulmonary and systemic complications associated with obesity, longitudinal randomized studies are needed to assess the impact of weight loss on metabolic syndrome and lung function.