GHRL and obesity due to melanocortin 4 receptor deficiency: This is in agreement with previous reports showing that ghrelin is unable to induce a hyperphagic response in diet-induced obesity (Gardiner et al., 2010; Perreault et al., 2004) and that this effect may be specifically due to ghrelin resistance in NPY/AgRP neurons in the ARC (Briggs et al., 2010).