In contrast with obesity, the pro-inflammatory cytokine-producing T helper type 1 (TH1) cells, CD8+ cytotoxic T cells, and NK cells that produce IFNγ (Kammoun et al., 2014; Deng et al., 2016) become abundant in the adipose tissue due to excess leptin, which leads to M1 macrophage accumulation and polarization (Deng et al., 2016). The gene discussed is LEP; the disease is obesity due to melanocortin 4 receptor deficiency.