Here's Why Overeating Makes You Dumber

You're at work having your usual productive morning. Your boss invites you to a leisurely lunch to discuss the company's quarterly earnings. You accept. You're famished and eat everything offered.  When you return to the office your production level has plummeted. You can hardly word an email, and you find yourself counting the hours until the day is over.

You discovered what the Ancient Romans knew centuries ago,  "A full stomach does not like to think." The proverb speaks for itself, but do you know why overeating actually makes you dumber? On average a person uses a great deal of their daily energy digesting and absorbing their food.  In fact, the body, when it's digesting, requires most of your blood flow. Notably, all of the functions of the body depend upon the blood. Therefore, where the blood flows, and doesn't flow in this case, affects your brain and in turn, your ability to concentrate.

The fact is, if digestion is to proceed normally, almost the entire energy of the body most lend itself to that work. During digestion, blood flow is sent to the digestive organs in large qualities. To do this, the body must constrict blood vessels in order to push blood toward the digestive organs. While this is happening there is less blood flow to other areas of the body, like the brain. Conversely, while the brain and muscles are active, digestion stops. 

The reality is this; every part of your body cannot have extra blood flow at the same time. If one part of the body gets more, another part of the body must get less. The body requires rest to digest. 

Eating between meals makes matters worse. Grazing, a common dietary practice dictated by the fitness industry is just plain bad advice. Cows graze. Humans eat. A cow that has a four compartment stomach grazes all day to get its daily intake of food, but a human with one stomach eats in this manner filling himself with enough food for one week. At some point., the body needs time to digest it. Unluckily, this process occurs when you sleep, making indigestion the number one cause of insomnia in the US, not only leaving you feeling dumber, but tired as well and prone to gaining weight.

Overeating and not properly digesting equal stress on the organs and body overall, which requires more blood flow taken from the brain.  Not surprisingly when we are tired we want to eat more. "When people were sleep deprived, they ate an extra 549 calories per day," says researcher Andrew Calvin, MD, MPH, a fellow in cardiovascular disease and assistant professor of medicine at Mayo Clinic, Rochester. 

Tips to stay sharp at work, before an exam or in class are:

  • Eat easily digested meals like a fresh juice or a piece of fruit for breakfast.
  • Lunch should be very light such as a smoothie, salad or soup.
  • The heaviest meal of the day should be at the end of the day, once you have rested. 
  • Eat three hours before bedtime to allow the body to digest.
  • Do not drink with meals, as this dilutes the much needed hydrochloric acid in the stomach, prolonging digestion.
  • If you don't have the time to digest, skip the meal.
  • Plan your meals around times you do have some downtime or rest afterward.


Reference:  Herbert, Shelton. "How to Eat." Accessed November 18, 2015.