[en] Ghrelin is a peptide hormone secreted by the stomach. It was initially described as a stimulant of growth hormone secretion. Soon, however, it was discovered to play an important role in feeding behaviour in animals and in appetite regulation in man: ghrelin stimulates appetite, and as such is an orexigenic peptide implicated in energy balance mechanisms and weight gain. Abnormal ghrelin activity leads to over- or underweight. Additionally, the efficacy of different treatment strategies against obesity seems to be related to modifications in plasma ghrelin levels. This review summarizes the current knowledge about ghrelin and its implications in obesity medicine.