Appetite and hunger are not the same.
People often think about hunger and appetite in the same way, as though the words were interchangeable. But the drivers within the body are quite different.
...is the body’s way of telling you of a physiological need for food. It occurs when blood glucose levels decline and hormones, such as ghrelin, rise. The body’s response to these fluctuations is symptoms of hunger which might include a rumbling belly. Other symptoms can include frowning, headaches, tiredness, rattiness. For me, I feel strain around my eyes when I am hungry.
Hunger drives us to eat in order to restore our body’s homeostatic levels. And the drive is very powerful indeed. When we are overhungry we will eat anything, ideally something full of fat and sugar. Once homestasis is achieved, satisfaction - hunger’s opposite - is reached.
...on the other hand is a psychological desire to eat, based more upon eating experiences, such as memories of good food, or other sensory cues such as taste, smell or texture of food.
While hunger occurs only when the body needs food, appetite can occur at any time, irrespective of the body’s need for energy. Appetite is why many still reach for pudding after a large meal. Appetite can be correlated with the hedonic (fun-loving) centres of the brain. In such cases, the physiological cues of satisfaction, such a full stomach, higher glucose levels and changes in hormone levels and mix, are overridden.
You know you are full, you know you are not hungry, but you eat the cake anyway. Not hunger, but appetite.