FOS and obesity due to melanocortin 4 receptor deficiency: Compared to the neuronal activation baseline (i.e., at the moment of the presentation of milk), an increase in the number of c-Fos-positive nuclear profiles after CM regardless of the whey:casein ratio was found in the hypothalamic paraventricular nucleus (PVN, the region whose lesion leads to overeating and obesity [46]), which is in line with previous reports examining c-Fos expression after food consumption [47].