The prevalence of obesity is rapidly increasing in the developed world and is a major drain on healthcare resources. It is associated with many serious medical conditions including diabetes, coronary heart disease, hypertension, osteoarthritis and several cancers [17,33]. Recommendations to diet and exercise are failing control the rising obesity levels. At present pharmaceutical based therapies are very limited and the only truly effective treatment is obesity surgery. Although effective, surgery is impractical as a wide spread treatment; therefore there is an urgent need for more effective pharmaceutical based therapies. Circulating hormones are known to play an important role in the regulation of appetite and energy expenditure. These hormonal systems represent valuable targets for the development of anti-obesity therapies. While there are many hormones that reduce appetite, ghrelin is the only known orexigenic circulating hormone.