A while back I posted about how carbs made me sleepy. That particular post has had more unique daily hits (means new people who haven't visited here before) than any other post on this blog. Apparently my problem is not unique. Actually, my 'problem' isn't really a problem.
Carbs spike the blood sugar in your blood stream. It also has something to do with seratonin and insulin production. If you ingest a huge amount of carbs all those levels spike then drop precipitously kind of like a sugar high. The spike in seratonin triggers your 'relax button' and you become sleepy.
Now, for those of us who try to adhere to a low carb lifestyle, our bodies adjust to having lower levels of blood sugar/insulin/seratonin. If we decide to indulge in carb rich foods we shock our system and, if you're like me, you pay for it dearly. The girls at work have been know to say "You had carbs today didn't you?" Apparently I act like a kid who's had too much candy when I've been eating carbs I'm not used to and then I become quite grumpy when I crash. I've scared my husband a couple of times by sleepign so soundly I barely breathe or move for several hours. Could be why I steer clear of the carbs most days.