At the cellular level, the lack of Mfn2 in POMC neurons decreased the activity of Complex I of the ETC and elevated ROS production leading to ER stress, suggesting that impaired mitochondrial fusion may promote a series of events conducive to interference of the melanocortin system and induction of oxidative stress, resulting in obesity. Here, POMC is linked to obesity due to melanocortin 4 receptor deficiency.