These phenotypes of rapid post-weaning obesity associated with hyperphagia and decreased metabolism are remarkably similar to those seen in the Nkx2.1iCre/+;Ngn3flox/flox mice of the current study, strongly suggesting that the primary cause of obesity in Nkx2.1iCre/+;Ngn3flox/flox mice is due to loss of hypothalamic Pomc. The gene discussed is POMC; the disease is obesity disorder.