Abstract

Leptin, insulin, and amylin are the so called adi−
posity 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 sig−
nals. If the amount of fat increases, however, lep−
tin resistance often develops. This explains why,
for example, the regulation mechanisms trigge−
red by leptin do not work effectively in obese
people. When used in combination, these hormo−
nes achieve a greater reduction in appetite and
therefore body weight; they thus represent an in−
teresting therapeutic option. Adiposity signals
influence other bodily functions too. Sufficiently
high concentrations of leptin and insulin are es−
sential for successful reproduction. From a teleo−
logical perspective, this seems to make a lot of
sense because reproduction (pregnancy, lacta−
tion) is a process that requires a lot of energy, so
that sufficient energy reserves are beneficial.