After eating, the workload of the gastrointestinal tract increases, leading to an increase in the amount of blood entering the gastrointestinal tract. Because the blood content of the whole body is constant, the increase of blood in the gastrointestinal tract will lead to the decrease of blood in other parts of the body, and therefore the blood supply to the brain will be relatively insufficient. When the blood supply to the brain is insufficient, the amount of oxygen carried in the blood will be reduced accordingly, leading to ischemia and lack of oxygen in brain cells, which will cause drowsiness and sleepiness in the body. In addition, after eating, blood sugar will suddenly rise, stimulating insulin secretion, which will then lead to a rapid drop in blood sugar, thus aggravating the symptoms of sleepiness.