Digesting food requires energy from the body. For this reason, the body feels tired after a large meal. The mouth, esophagus, stomach and intestines work hard to control the nutrients and food entering the body and transport them to the right location. The action of eating is associated with weight gain, but it requires high amounts of energy expenditures.
Symptoms
Drinking coffee in the morning energizes people for their daily activities. However, after a heavy lunch, some people have a hard time focusing or staying awake. This usually happens after lunch or dinner, and it affects work and school. The symptoms are yawning and feeling as though a nap is needed. Some people only feel the symptoms after eating certain foods. The symptoms have generated the term "food coma."
Digestion
The source of the food coma and lack of energy comes from the work needed to digest food. It also has to do with the brain chemistry after eating a large meal. First, the stomach is triggered to create acids to help digest food. The stomach also controls the rate at which food is dropped into the intestines. The pancreas then produces enzymes to degrade and absorb the nutrients. The nutrients absorb into the intestines and cause a surge in glucose levels in the blood.
Brain Chemistry
The second reason the body feels tired are the changes in chemistry in the brain. Brain cells only use sugar for energy, so when the body is hungry, the brain produces a chemical called orexins. According to the University of Manchester, orexins keep the dieter awake and alert to instinctively find food. However, when a meal is consumed, the brain no longer needs those chemicals, so it stops producing orexins. This lowers alertness and creates the sleepy feeling after a meal.
Tryptophan
Tryptophan is an amino acid that converts to serotonin in the brain. Serotonin is the "happy" neurotransmitter. Serotonin also makes a person feel content and drowsy. Tryptophan is in proteins. The most common source for tryptophan is turkey, which is why turkey sandwiches and Thanksgiving make people feel sleepy afterward.
Considerations
People who have severe drops in energy levels after eating are urged to keep a journal and make note of which foods cause the highest amount of energy loss. Some people may feel more drowsy after pastas, breads and heavy meals. For dieters who struggle after lunch, it is more beneficial to focus on vegetables and fruits with low amount of proteins and fats during daytime meals. A journal will also help identify any other foods that cause a food coma.
