The human gut is a world full of microbial flora. There are about 1000 kinds of bacteria living in the human intestine, collectively referred to as the intestinal flora. The total weight is about 1.5 kilograms. The number of cells is 10 times the total number of human cells. The total number of genes encoded is 100 times of the total number of human genes. The function of the intestinal microflora profoundly affects the health of the human body.
Studies have found that in people who have difficulty losing weight, intestinal bacteria are better at using carbohydrates to provide more energy to the body, which means that gut microbes provide an important direction for weight loss.
A study of mice at 2013 found that mice that had undergone "intestinal bacterial transplantation" had increased body weight and fat mass more than those who had been transplanted with lean human bacteria.
A study of people at 2015 found that bariatric surgery can lead to long-term changes in intestinal bacteria, which is conducive to weight loss.
An article, Seeking an Obesity Cure, Researchers Turn to the Gut Microbiome, published in The New York Times, said that Dr. Elaine Yu, an endocrinologist at Massachusetts General Hospital in Boston, and her research team is exploring whether it can stimulate metabolism and potential weight changes through fecal microbial transplant (FMT) therapy, transferring intestinal bacteria from lean donors to the intestines of obese patients. The team recruited 24 obese men and women with insulin resistance and 4 lean donors. Half of the obese subjects took a special frozen capsule containing feces from the donor weekly, while others received a placebo. However, after 12 weeks, the results showed that the subject's metabolic health did not improve. But other small studies have found that fecal transplant capsules alter the microbiome of obese subjects and cause positive changes in their bile acids and digestive aids produced by the liver.
Overall, these small studies are too small and do not have enough time to assess changes in subject weight. More research is needed to explore whether the use of intestinal microbes to reduce body weight is effective.