Yawning is a natural occurance.

• Yawning is a natural, involuntary reaction. For most of the population, yawning is associated with a person being tired or sleepy. The consensus on why we yawn seems to be that a yawn is caused from a lack of oxygen to the brain. This lack of oxygen automatically sends a message from the brain to the other parts of body. This message will then produce a yawn, which draws needed air into the lungs. By oxygenating the blood, the body will have more energy.
  
  

Posture and blood-sugar levels after eating

• Large meals can cause yawning.
  
  Poor posture can cause yawning. When a person is in a slouched position, pressure is put on the lungs, which will not allow them to fill with air while breathing. This is even more evident after eating. The stomach is full, which will put pressure on the lungs from the abdominal area. After a big meal, the body may relax to a slumped position, which puts pressure on the lungs from the ribs and chest area. When a person has overeaten, and is very full, this puts even more pressure on the lungs and may cause excessive yawning after eating.
  
  The tiredness or drowsy feeling you get after eating a full meal will also affect your blood-sugar level. This, too, may cause excessive yawning by creating a chemical imbalance in the body. The yawing and sleepy sensations may continue until the body has a chance to level out the sugar imbalance and return the sugar levels to normal.
  
  

Medical conditions that cause yawning

• H pylori
  
  There are conditions, however, that may cause the need for yawning. If a person yawns four times within one minute, it is considered to be excessive. If the yawning persists and occurs in an abnormal amount of time, you will need to seek medical attention to rule out a more serious condition.
  
  One condition that can cause excessive yawning after eating is helicobacter pylori. This infection has been closely linked to gastric disorders such as cancer and ulcers. Once the problem has been diagnosed and it has been found that helicobacter pylori is present, antibiotics are given and the excessive yawning after eating should cease.
  
  

Yawning is caused from central nervous disorders.

• Central Nervous System
  
  There are other, more serious conditions that are thought to cause excessive yawning, especially after eating. Yawning may occur and be related to those suffering from migraine headaches, Parkinson's disease, tumors, psychiatric diseases and some infections. The majority of these problems are directly related to the central nervous system.
  
  Other central nervous disorders that may cause excessive yawning appear in those who are suffering from epilepsy, encephalitis, multiple sclerosis and supranuclear palsy. Yawning may also be related to the drugs that are taken for these disorders. Those drugs can amplify yawning, especially after meals.
  
  

Yawning serves a purpose.

• Science has not figured out conclusively why a person yawns. Experts agree however that yawning does serve a purpose concerning how the body functions. Testing for specific ailments to rule out a more serious condition is the only way to diagnose what would cause a person to have excessive yawning after eating.
  
  Cite Hermanowicz N. Cranial nerves IX (glossopharyngeal) and X (vagus). In: Goetz CG, ed. Textbook of Clinical Neurology. 3rd ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 13.
  
  LeWinter MM. Pencardial diseases. In: Libby P, Bonow RO, Mann DL, Zipes DP, eds. Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine. 8th ed. Philadelphia, Pa: Saunders Elsevier;2007:chap 70.
  
  http://www.nlm.nih.gov/medlineplus/ency/article/003096.htm