Composed mainly of bacteria, along with archaea, fungi, and viruses, the trillion-member community that resides in the human gastrointestinal tract has emerged as a key regulator of host metabolism, playing a crucial role in the pathophysiology of obesity by contributing to increased energy harvesting and storage, affecting adipose tissue composition and fat mass gain, as well as providing low-grade inflammation and insulin resistance [6]. Here, INS is linked to obesity due to melanocortin 4 receptor deficiency.