Meanwhile, smoking and obesity bear a complex relationship with COPD aggravation: adipose tissue is a critical place where cytokines (TNF-a and IL-6) form; adiponectin declines with a higher degree of obesity, which would enhance the resistance of insulin, circulate radicals and oxidative stress, and aggravate pulmonary inflammation [48–50]. This evidence concerns the gene IL6 and obesity due to melanocortin 4 receptor deficiency.