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Manipulating Gut Bacteria May Treat Obesity

Gut bacterial ratios change in obese people on a low-fat diet and correlates with weight loss

THURSDAY, Dec. 21 (HealthDay News) -- Obese people have a different composition of gut bacteria than lean people, and a low-fat or low-calorie diet leads to changes in the ratios of these bacteria and weight loss, according to two studies in the Dec. 21/28 issue of Nature.

In the first study, Jeffrey I. Gordon, M.D., and colleagues from Washington University in St. Louis, sequenced the DNA of microbes found in the distal gut of genetically obese mice and normal lean mice. They found that the obese mice had a higher ratio of Firmicutes to Bacteroidetes bacteria (the two beneficial types in the gut), while the reverse was true for the lean mice. The bacteria in the obese mice were more efficient at releasing energy from food. Transplanting gut bacteria from the obese or lean mice into the guts of lean germ-free mice showed that mice colonized with the obese bacteria had significant increases in body fat after two weeks.

In the second study, the same group randomly assigned 12 obese people to a fat-restricted or carbohydrate-restricted diet and monitored their gut bacteria over one year by examination of stool samples. They found that the ratio of Firmicutes to Bacteroidetes bacteria was higher than lean controls at the beginning of the study, but the ratio decreased with time with both diets. The increase in Bacteroidetes bacteria correlated with weight loss, not dietary calorie content, according to the study.

"The dynamic linkage between adiposity and gut microbial ecology described here, together with our results in mice, indicates that manipulation of gut microbial communities could offer another approach in the treatment of obesity," Gordon and colleagues conclude.

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