If you find yourself hungry shortly after a meal you may be eating a carb rich diet that causes your blood Sugar level to rise very quickly and consequently drop low shortly after. The result of a sharp drop in blood Sugar is your feeling hungry even with a belly full of food. I went through the same thing a few years back. I got it all sorted with a help of a nutritionist. A bonus with learning this little trick of getting my blood Sugar level at even kilter, was loosing the weight I wanted and keeping it off the past 6 years.