Circulating factors are important in regulating energy balance. It has long been recognized that the adipose hormone, leptin, reduces food intake by specific CNS pathways. Gut hormones have also been shown to be major regulators of appetite, acting both in the brainstem and hypothalamus. In addition, they have been found to markedly influence energy expenditure. Obesity is associated with a reduced gut hormone release but the mechanism is unknown. In man, this change may perpetuate or contribute to obesity. This meeting will address the physiological importance of circulating hormones in the regulation of energy balance. We will explore the mechanisms involved, their disturbance in obesity and therapeutic possibilities. Obesity produces over 6,000 excess deaths a week in the USA alone, yet there is no really effective treatment. This meeting is to advance the most promising approach to a safe practical therapy seen in the last 50 years.