In this study, we tested whether HF diet affects BMAL1 function in an insulin-dependent manner by analyzing BMAL1 activity in the liver as well as in several extra-hepatic tissues under conditions of diet-induced obesity with or without application of the thiazolidinedione, rosiglitazone (ROSI). The gene discussed is BMAL1; the disease is obesity due to melanocortin 4 receptor deficiency.