Leptin, insulin, and amylin are the so called adiposity signals; they inform the brain about the amount of fat deposited in the body. Leptin is produced and secreted directly by the fat cells, depending on the amount of body fat, whereas insulin and amylin originate from the pancreas. All 3 adiposity signals reduce food intake and increase energy release. Part of their effect is to increase the action of physiological satiation signals. If the amount of fat increases, however, leptin resistance often develops. This explains why, for example, the regulation mechanisms triggered by leptin do not work effectively in obese people. When used in combination, these hormones achieve a greater reduction in appetite and therefore body weight; they thus represent an interesting therapeutic option. Adiposity signals influence other bodily functions too. Sufficiently high concentrations of leptin and insulin are essential for successful reproduction. From a teleological perspective, this seems to make a lot of sense because reproduction (pregnancy, lactation) is a process that requires a lot of energy, so that sufficient energy reserves are beneficial.