In addition, orexin and serotonin receptor gene expression studies in obese and obesity‐resistant animal models, and metabolic studies with double mutant mice (specific orexin and serotonin receptor KO) would be beneficial to test whether there is an optimal balance between OXA/serotonin systems to maintain an ideal metabolic state. Here, HCRT is linked to obesity due to melanocortin 4 receptor deficiency.