Why do we get sleepy after eating a big meal?
The popular medical opinion is that your body rushes blood to your stomach because it's busy digesting such large quantities, but personally I don't buy that.
I think it's your brain saying, "Ok, clearly you have no idea what you're doing. You don't have any idea how much food is appropriate, or what kind of food you should be eating. Now go to sleep, try again tomorrow."*
This mental mechanism is the same one that gives you an aversion to something you got food poisoning from and makes you throw up when you've had too much to drink. Wired into your mind is a patient parent desperately trying to save you from your own dumb ass.
As you may imagine, I have used this concept to make some very passionate defenses for avoiding spinach, seaweed, turnips, and green beans. My longstanding hatred of each one, I reason, is not a childish dislike for vegetables, but rather my own mind insisting that these things are poison to this particular body.
*So then the minds of most men are trying to save them from watching baseball?