Maintenance of energy homeostasis requires the coordination of systems that regulate feeding, autonomic and endocrine functions with those that govern an appropriate state of arousal. The hypothalamus play a critical role in maintaining energy homeostasis by integrating and coordinating these systems. Recent studies have suggested that orexin-containing neurons in the lateral hypothalamic area constitute an important central pathway that promotes adaptive behavioral and arousal responses to metabolic and environmental signals. This article review recent studies on orexin to suggest that orexin neurons play a significant role in feeding and arousal regulation, possibly by coordinating the complex behavioral and physiological responses of these complementary homeostatic functions.