Significant changes to the bacteria that live in our guts may be partially behind the rapid weight-loss success of patients who undergo gastric bypass surgery, a new study in mice shows.
Gastric bypass is a form of weight-loss surgery performed on morbidly obese people. The stomach is made smaller, to about the size of the egg, so that people feel full faster and are not able to eat as much.
Because gastric bypass is extremely invasive, understanding the mechanisms changing the microbial community in patients’ guts after surgery could help scientists design less invasive ways to help dangerously obese people lose weight.
New research published Thursday, March 27, in the journal Science Translational Medicine, suggests that some of the effects of gastric bypass, like decreased weight and body fat, are aided by changes to microbes — bacteria, viruses, and yes, even fungus — in everyone’s intestines.
To see how gastric bypass affects microbes in the distal gut, which is where the small intestine meets the large intestine, researchers divided obese mice into three of groups: those that received gastric bypass surgery; those that continued to eat a high-fat, high-carb diet; and those that ate a reduced-calorie diet.
Although the bypass mice and those on a restricted diet lost the same amount of weight, the animals who received surgery had changes to their gut bacteria. They showed an increase in bacterial populations associated with healthy, lean humans and a decrease in bacterial populations associated with obese people. Two other groups of bacteria were increased, but their function is still not known.
The gut bacteria of the dieting mice didn’t change.
To confirm their results, altered gut microbes from each of the three mice groups were transferred into the gastrointestinal systems of skinny mice. After two weeks, the mice who received microbes from the mice that had gastric bypass had lost weight, even though they ate the same amount of food as the control mice.
There was no change in weight of the mice who were treated with microbes from either the mice on high-fat diet and the calorie-restricted diet.
This suggests that gastric bypass — and not calorie restriction or weight loss in general — triggers these microbial changes. And these changes are one way that gastric bypass causes weight loss.
“Our study suggests that the specific effects of gastric bypass on the microbiota 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,” Lee Kaplan, a senior author of the paper, said in a statement.
NOW WATCH: Briefing videos
Business Insider Emails & Alerts
Site highlights each day to your inbox.