The old hypothesis regarding appetite control and the body was that the hormone leptin regulated satiety. If the body produced more leptin, appetite would be suppressed by sending a signal to a particular part of the brain called the ARC (arcuate nucleus). ARC is in an area of the hypothalamus that controls energy balance.
However, new research shows that other parts of the brain have receptors for leptin. The LHA (lateral hypothalamic) area is one such example, and it has strong connections to the dopamine system in the VTA (ventral tegmental area) which is responsible for the brain’s reward system. Dopamine is the chemical signal used by the brain for rewards.
The new hypothesis shows that someone who has a higher amount of dopamine under normal circumstances may be more resistant to food temptations. Also, someone with naturally low levels of leptin may eat more to stimulate the reward system to bring dopamine levels to what feels “normal”.
The new study shows that leptin injected in the LHAs of rats causes the animals to eat less and lose weight. Leptin action in the LHA also raises dopamine content in the brains of otherwise leptin-deficient animals.
We are moving closer to a day when an eating disorder can be dealt with by simply taking a pill. However, it will take several years and more studies like this one before a product is commercially available.