According to our results, ER stress was enhanced in BAT of HFD-treated mice, as shown by the increase in the mRNA expression of Bip and Chop. In our study, obesity-related pathological processes such as apoptosis, fibrosis, inflammation or ER stress are more evident in obese WAT than in BAT. Here, DDIT3 is linked to obesity due to melanocortin 4 receptor deficiency.