Sun et al. found that GHSR knockout mice have a similar susceptibility to diet-induced obesity compared to wild-type mice upon exposure to HFD as adults (Sun et al., 2008); however, GHSR knockout mice manifest reduced age-associated obesity mainly due to reduced adiposity and increased thermogenesis (Lin et al., 2011; Ma et al., 2011). Here, GHSR is linked to obesity due to melanocortin 4 receptor deficiency.