Ghrelin receptor (Ghsr) knockout mice have been shown to be resistant to HFD-induced obesity (73) and mice lacking active ghrelin (lacking the gene, Goat, that encodes ghrelin O-acyl transferase which acylates ghrelin) are resistant to obesity when fed a high-sugar diet (74). This evidence concerns the gene GHRL and obesity due to melanocortin 4 receptor deficiency.