Leptin promotes the proliferation and activation of NCM and IM favouring metabolic diseases, such as obesity [45,48], thereby leptin action induces higher BMI and REE as an effect of the chronic low-grade inflammation per se, which could explain the increase of β2AR expression on monocytes and its association with BMI. This evidence concerns the gene ADRB2 and obesity due to melanocortin 4 receptor deficiency.