The reason why you started to feeling tired after eating is because your body's got an imbalance. It's picked up some sort of infection or overgrowth - knocking it out of balance.
So now, when you're eating food, the food's going down into your small intestine and this creates inflammation inside your intestinal lining. Once you get inflammation in your intestinal lining, undigested food particles and other wastes can pass through into the blood.
When this happens, it creates inflammation inside your blood because your body's reacting to the undigested food particles and toxins. The body thinks it's a virus trying to attack the body.
Once you have inflamed blood, you got inflamed blood supplying all your body - which is why you feel tired and fatigued after eating.
What we need to do - get rid of the underlying infections or overgrowth that's creating your issues.