Neuromedin U is a neuropeptide, first isolated from porcine spinal cord and expressed widely in the gastrointestinal, genitourinary and central nervous systems. Neuromedin U has potent contractile activity on smooth muscle and this activity is believed to reside within the C-terminal portion of the peptide, which is highly conserved between species. Neuromedin U (NMU) is a hypothalamic neuropeptide that regulates body weight and composition. Some studies indicate that NMU plays an important role in the regulation of feeding behavior and energy metabolism independent of the leptin signaling pathway. These characteristic functions of NMU may provide new insight for understanding the pathophysiologic basis of obesity.