Actually, it's not like this. Many people think that after meals, the whole body blood is concentrated in the digestive system to help gastrointestinal peristalsis and digestion, which will cause insufficient blood supply to the brain and make the brain hypoxic, and people will feel sleepy. Actually, this is unscientific.
As the most important organ of the human body, the human body will give priority to ensuring the blood supply to the brain. If, as many people think, the brain is deprived of oxygen because of reduced blood supply, then that person should feel dizzy, not just sleepy. Foreign studies have indeed found that the blood flow in the brain after meals has not decreased but increased.
Then why is there a "rice sleepy"?
This is mostly related to the endocrine status of the human body after meals. When people eat high-carbohydrate foods, their blood sugar will rise, which will inhibit the secretion of an appetite hormone by the inferior colliculus A. When the content of this protein hormone is low, people will feel tired and sleepy.
In addition, American researchers found that the secretion of cholecystokinin may be related to postprandial drowsiness. The researchers tested the secretion of cholecystokinin and the score of the sleepiness scale before and after meals, and found that there was a positive correlation between them, that is, the more cholecystokinin secreted, the more sleepy people were. If the food you eat is too greasy, you will secrete a lot of cholecystokinin, which may also be the reason why you feel "sleepy" after meals.