The administration of melatonin along with the high fat diet, did not modify the values obtained in obese rats at 09:00 a.m. Moreover, Melatonin administration prevented the effect of obesity on HO-2 gene expression (ANOVA p < 0.009 vs. obese group) at 01:00 a.m. Here, HMOX2 is linked to obesity due to melanocortin 4 receptor deficiency.