By Lauran Neergaard
WASHINGTON: Call it a hidden ally: The right germs just might be able to help fight fat.
Different kinds of bacteria that live inside the gut can help spur obesity or protect against it, say scientists at Washington University in St. Louis who transplanted intestinal germs from fat or lean people into mice and watched the rodents change.
And what they ate determined whether the good germs could move in and do their job.
Thursday’s report raises the possibility of one day turning gut bacteria into personalized fat-fighting therapies, and it may help explain why some people have a harder time losing weight than others do.
“It’s an important player,” said Dr. David Relman of Stanford University, who also studies how gut bacteria influence health but wasn’t involved in the new research. “This paper says that diet and microbes are necessary companions in all of this. They literally and figuratively feed each other.”
The research was reported in the journal Science.
Washington University graduate student Vanessa Ridaura took gut bacteria from eight people — four pairs of twins that each included one obese sibling and one lean sibling. One pair of twins was identical, ruling out an inherited explanation for their different weights. Using twins also guaranteed similar childhood environments and diets.
She transplanted the human microbes into the intestines of young mice that had been raised germ-free.
The mice who received gut bacteria from the obese people gained more weight — and experienced unhealthy metabolic changes — even though they didn’t eat more than the mice who received germs from the lean twins. Mice that harbored gut bacteria from a lean person were put in the same cages as mice that harbored the obesity-prone germs.
What happened was a surprise. Certain bacteria from the lean mice invaded the intestines of the fatter mice, and their weight and metabolism improved. But the trade was one-way — the lean mice weren’t affected.