While whole body insulin sensitivity was not different between WT and GPRKO mice (Fig. 2D), WT female mice fed a HFD had higher insulin (Fig. 2E) and leptin (Fig. 2F) levels than those in GPRKO female mice (p < 0.05; Fig. 2E), which are typically associated with obesity and insulin resistance. Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.