GDF15 and obesity due to melanocortin 4 receptor deficiency: Treatment or overexpression of GDF15 exerts protective effects against obesity and insulin resistance in mice fed a high-fat diet and in non-human primates with spontaneous obesity (Macia et al. 2012, Tsai et al. 2013, Chrysovergis et al. 2014, Mullican et al. 2017), while GDF15 knockout mice were more susceptible to obesity induced by a high-fat diet, exhibited worse glucose tolerance, and had a lower metabolic rate compared to wildtype mice (Tran et al. 2018).