The small intestine is the main place where the body absorbs food. After the initial digestion in the stomach, most of the food we eat is fully decomposed under the action of digestive juices such as pancreatic juice, bile and small intestine fluid, and then absorbed by the mucous membrane of the small intestine and converted into the nutrients and energy needed by the body. In addition to the small intestine itself, the intestinal flora is also an important part of the digestive system. There are a large number of flora distributed inside our intestines, which not only participate in the synthesis of a variety of vitamins needed by the body, but also promote absorption, which is one of the important factors affecting our weight and digestive ability. Under normal circumstances, the flora parasitic in the intestine can coexist with us peacefully, maintaining a dynamic balance. However, if we overeat for a long period of time, it will lead to changes in the division of intestinal flora, making our absorption ability greatly enhanced, and we will get more nutrients and energy than others with the same amount of food. In addition, some changes in the number of flora can also directly lead to obesity. Studies have been conducted both at home and abroad, and they found that when the intestinal flora of obese people were implanted into mice, the mice would soon become fat as well, but further research is needed on exactly those kinds of flora. Currently, intestinal flora has been included in the treatment of obesity, such as gastric bypass surgery in weight loss metabolic surgery to enhance the treatment effect by improving intestinal flora. This procedure, by absolving the large part of the stomach, the duodenum and the first jejunum, disables the flora on the corresponding intestinal tract as well, significantly reducing the patient’s absorption capacity and obtaining good weight loss results. It is also possible to perform a sleeve gastric + jejunostomy, a surgical procedure that reduces the size of the stomach while also displacing a portion of the intestine, which also has the effect of improving the flora.