The discovery of ghrelin has resulted in the development of approaches to appetite, enabling a better understanding of the mechanisms regulating appetite through molecular analyses. Ghrelin is a 28-amino acid peptide that was isolated from the stomach only a decade ago, and has recently been investigated as a potential therapeutic endogenous agent. This peptide increases appetite, adjusts energy balance, suppresses inflammation, and enhances the release of growth hormone from the pituitary gland. Although many bioactive substances such as peptide YY, leptin, adiponectin and obestatin are involved in appetite control, ghrelin is the only known peptide to signal starvation information from a peripheral organ to the central nervous system, contributing to an increase in appetite. Clinical trials have revealed the effectiveness of ghrelin in increasing lean body mass and activity in cachectic patients. As shown in clinical research on humans and basic research using animal models, cachexia often occurs in response to excess release of proinflammatory cytokines and induces further appetite loss, which aggravates the physiological status of underlying diseases. Ghrelin functions as a protector against the vicious cycle of the cachectic paradigm through orexigenic, anabolic and anti-inflammatory effects, so administration of ghrelin may be able to improve quality of life in cachectic patients. We show here a significant role of ghrelin in the pathophysiology of cachectic diseases and the possibility of clinical applications.