RSPO1 and obesity due to melanocortin 4 receptor deficiency: To further investigate the potential anti‐obesity effect of blocking endogenous Rspo1, we generated Rspo1 knockout (Rspo1−/−) mice (Figure S5A, Supporting Information) and confirmed that endogenous Rspo1 was effectively deleted in Rspo1−/− mice (Figure S5B, Supporting Information).