M1 macrophages accumulate with obesity and secrete pro-inflammatory cytokines such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α) (Amano et al., 2014; Pincu et al., 2015; Batra et al., 2018), and are characterized by the presence of inducible nitric oxide synthase (iNOS) and cluster of differentiation 86 (CD86) (Chen et al., 2018; Liu et al., 2018), which have been directly linked to IR (Appari et al., 2018). This evidence concerns the gene NOS2 and obesity due to melanocortin 4 receptor deficiency.