Cravings are influenced by the area of the brain stem called the parabrachial nucleus.
A common finding when people try to lose weight is that cravings for carbohydrates increase. This is especially true when the body is under stress making it harder to resist snacks and excess calories.
The hypothalamus regulates appetite by receiving feedback from hormones such as leptin, insulin and ghrelin.
The hypothalamus uses this feedback to automatically control your hunger. However, when body weight goes down the hypothalamus unfortunately increases appetite significantly.
Fullness is automatically regulated in the area of the brain called the nucleus of the solitary tract. It does this by monitoring signals from the gut and hormone levels in the blood. It is also this part of the brain that determines portion size and lets you know when you are full.
It is this area of the brain stem that leads to someone never feeling satisfied with food and typically leads to overeating.