Correspondence: David H St-Pierre Department of Kinesiology, Universite du Quebec a Montreal, 2888 Succursale Centre-Ville, Montreal, Quebec H3C 3P8, Canada Fax +1 514 987 6616 Tel +1 514 987 3000 ext 5150 Email st-pierre.david_h@uqam.ca Abstract: Acylated ghrelin is one of the few peptides known whose isolation and characterization follow the description of its receptor and its basic biological functions. Characterized initially for its somatotrophic properties, ghrelin was shown later to exert various effects on other important physiological functions in mammals, such as appetite, gastric acid secretion, gut motility, insulin sensitivity, adiposity, and energy expenditure. Further, ghrelin influences cardiac function, reproduction, and the immune system as well. Here we present an overview of the discovery and subsequent development of ghrelin as an important peptide hormone involved in the control of energy metabolism in humans and other mammals. Recently reported effects of acylated ghrelin on glucose/lipid uptake, de novo lipogenesis, gluconeogenesis, lipid-droplet formation, fatty acid transport into mitochondria, and mitochondrial activity are particularly emphasized and discussed.