Feeling hungry after eating could be due to leptin resistance. Leptin, a hormone produced by body fat, controls whether or not you feel full after eating. This is because the body secretes leptin when you've had enough to eat and tells your brain you're full.
What can increased appetite mean?
In some cases, an increase in appetite can be a sign of an abnormal condition, such as some endocrinologic conditions, including diabetes, hyperthyroidism, and Graves' disease. Increased appetite may also be seen in certain emotional or psychiatric conditions, as well as a response to stress, anxiety, or depression.
What is it that makes you feel hungry?
Several other hormones influence hunger. Two major ones which tip the balance between hunger and fullness are leptin and ghrelin. Leptin is released from the body's long term fat stores, which we all have, and suppresses hunger while ghrelin causes stomach rumblings as a physical reminder to eat.