Zucker fatty rats, in which a leptin receptor mutation produces hyperphagia and obesity, have markedly increased SAM in the liver13 and pancreas.14 Conversely, conditions characterized by inability to maintain cellular energy levels, such as septic shock and hypoxia, result in MAT inactivation (reviewed in Mato et al.1). Here, LEPR is linked to obesity due to melanocortin 4 receptor deficiency.