To find the cause of the "dessert stomach," the researchers investigated the reaction of mice to sugar and found that completely satiated mice still ate desserts. Investigations of the brain showed that a group of nerve cells, the so-called POMC neurones, are responsible for this. These neurones become active as soon as the mice were given access to sugar which facilitated their appetite.
When mice are full and eat sugar, these nerve cells not only release signaling molecues that stimulate satiety, but also one of the body's own opiate: ß-endorphin.
This acts on other nerve cells with opiate receptors and triggers a feeling of reward, that causes the mice to eat sugar even beyond fullness.
This opioid pathway in the brain was specifically activated when the mice ate additional sugar, but not when they ate normal or fatty food.
