Leptin--from the Greek word "leptos", meaning thin--is a protein hormone that affects the regulation body weight, metabolism and reproductive function.

Leptin is encoded by the obese (ob) gene and is expressed by adipocytes--or fat cells- and acts on the central nervous system to suppress food intake and increase energy consumption.

References

Duell PB, Weigle DS, Connor WE.Effects of energy intake on the regulation of plasma leptin concentrations.Am J Clin Nutr. 1998 Dec;68(6):1304.