IGF1 and obesity due to melanocortin 4 receptor deficiency: Indeed, low affinity binders may have profound effects on the pathogenesis of obesity and insulin resistance, as shown in the case of insulin-like growth factor binding proteins (IGFBPs) comprising both insulin-like growth factor (IGF) high- and low-affinity binders (Kim et al., 1997; Ruan & Lai, 2010).