Treatment of rodents fed a high-fat diet with recombinant growth differentiating factor 15 (GDF15) reduces obesity and improves glycaemic control through glial-cell-derived neurotrophic factor family receptor α-like (GFRAL)-dependent suppression of food intake<sup>4-7</sup>. The gene discussed is GDF15; the disease is obesity due to melanocortin 4 receptor deficiency.