An intact hypothalamic melanocortin pathway is critical for the homeostatic control of energy balance, appetite and body weight, and interruptions to signalling across parts of this pathway have been demonstrated to lead to obesity, often resistant to treatment through energy restriction.9 The central hypothalamic melanocortin-4 receptor (MC4R), therefore, constitutes a distinctly validated therapeutic target for the treatment of genetic obesity. This evidence concerns the gene MC4R and obesity due to melanocortin 4 receptor deficiency.