LEP and obesity due to melanocortin 4 receptor deficiency: Obesity is defined by the World Health Organization as an “excessive or abnormal fat accumulation that presents a risk to health.” Weight gain is associated with marked hyperplasia of the white adipose tissue and substantial changes in the function of adipocytes that start to secrete a number of bioactive molecules collectively referred to as adipokines (leptin, adiponectin, and a multitude of pro- and anti-inflammatory cytokines) (Lehr et al., 2012; Aguilar-Valles et al., 2015).