Work in rodents and non-human primates has demonstrated substantial pharmacological benefits of FGF21 on a range of metabolic complications linked to obesity, including a reduction in fat mass and alleviation of hyperglycaemia, insulin resistance, dyslipidaemia, cardiovascular disorders and non-alcoholic steatohepatitis (NASH)32. The gene discussed is FGF21; the disease is obesity due to melanocortin 4 receptor deficiency.