Sleepy after eating
It’s completely normal to feel sleepy after eating a big meal because your blood flows to your stomach in order to digest all the food you have eaten. That is why you are not in mood to do anything after a huge meal. It is even advisable an hour of rest before doing anything else.
From my point of view that’s exactly the problem with big meals. After eating hundreds of fat, carb and protein calories, your body’s “warehouses” (your fat) will be filled even more because these calories have not been used for anything productive while you are resting after the big meal. That’s why it is far better to eat 5, 6, 7 tiny meals a day because (1) you will burn those calories straight off and (2) you will be more energized and productive throughout the day without those huge energy drops.
By eating 7 small meals you could even eat 20-30% more calories a day without getting fatter. A rule of thumb to calculate a small meal is that after eating a small meal you still feel just a bit hungry. This tiny hunger is like a primate trigger (to search for food) that will keep you going throughout the day.
Less is sometimes more. Think about it and don’t fall asleep!