Why does my heart pound so hard after eating?

Heart pounding. Depends. This may be a problem. With eating, the digestive process diverts a good deal of blood and shunts it to the intestines. If the heart becomes short on its blood supply it can cause heart pounding and symptoms. Best to discuss this with your doctor and get an examination.
See your Dr. Sometimes after a large meal the blood rushes to your stomach and bowels, this causes a drop in your blood pressure, to make up for that your heart rate will go up. If you also eat a diet high in carbs and fat, your sugar and triglyceride level will suddenly spike in your blood stream causing these symptoms. You should get blood work done to check your glucose, thyroid and cholesterol level.