Why you feel tired, sleepy or sluggish after eating is all about blood distribution. And you likely don’t notice this listlessness for about a half hour after your meal because that’s about how long it takes for your small intestine to come into digestion play.
Your small intestine is the major site for digestion and absorption of nutrients. When not active, or at rest, it only uses about 20% of your total blood output. However, after a large meal this amount nearly doubles.
And where blood goes, so goes the basics of energy production oxygen and glucose. Consequence is energy deprivation of the rest of you. So, it’s the rush of blood to your stomach yielding that feeling of tiredness, sleepiness or sluggishness.
On the other hand, if you exercise during the digestion process, then the redirected blood flow reduces to roughly half. And as you might expect, food absorption is delayed.
The only two organs not significantly affected by this tide change are your brain and heart. Neither receives sympathetic nervous system influence to adjust circulation, thus no portion of their blood supply is involved in the feeding frenzy blood control mechanism.
There are also some other slightly influential reasons for feeling weak after eating, like:
- food allergies
- gluten intolerance
- lactose intolerance
- sugar & other carbs influence brain chemistry
- sugar has calming effect due to serotonin increase
- carbohydrate, protein mixed meals cause tryptophan creation for serotonin production
To avert that tired, sleepy or sluggish feeling, you could try eating smaller meals more often. Or continue to plan on a rest stop post feast.