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Why You're Fat

Could Transferring Gut Bacteria Help People Lose Weight?

You can exercise and eat right (and even get surgery), but it seems like a good chunk of your weight is determined by which kind of bugs are living in your intestines.

Anyone for a fecal transplant? Yes, you read that correctly, and it does mean what it says. Recently, scientists have become increasingly interested in transferring stool from healthy guts to unhealthy ones. Research shows that the procedure can rebalance gut bacteria, and help fight superbugs like Clostridium difficile, which kills 14,000 in the U.S. every year. Some researchers are even working on a "robo-gut" to create "synthetic stool," as we wrote about here.

And now research is raising another possibility for bacterial transfers: losing weight.

Researchers at Harvard and Massachusetts General Hospital wanted to find out why people who receive gastric bypass surgery lose so much weight. They suspected that it was linked to changes in the microbial makeup of their stomachs. But they didn’t know whether it was the result of surgery itself, or from losing weight afterwards. To understand, they took two sets of mice, and gave one set full gastric operations, and another "sham" procedures, where they opened up the intestines, but closed them again. When they transferred stool from the first set (which had received the real operation) to sterile mice, the latter lost about 20% of the amount from the full operation. In other words, transferring bacteria seemed to have about a fifth of the effectiveness of surgery, with none of the unpleasantness.

"Our study suggests that the specific effects of gastric bypass on the microbiota [in the stomach] contribute to its ability to cause weight loss and that finding ways to manipulate microbial populations to mimic those effects could become a valuable new tool to address obesity," says Lee Kaplan, director of the Obesity, Metabolism and Nutrition Institute at Massachusetts General Hospital, one of the authors of the paper.

The researchers caution that treatments are unlikely to appear for years, and even then, they are unlikely to be aimed at the marginally overweight. More likely, treatments would be aimed at reducing the number of people who have to undergo bariatric work every year—about 200,000 a year in the U.S. at the moment.

Still, the research adds further grist to the idea that balancing the gut’s micro-chemistry is key to many aspects of health. And it’s not hard to see how microbial health could be a big thing going forward—stool transplants, or no.