WEDNESDAY, Dec. 20 (HealthDay News) -- Obesity not only disrupts a person's health, it also disrupts the makeup of healthy germs inside the digestive tract, a new study suggests.

While the significance of the finding isn't immediately clear, it could potentially lead to new treatments for overweight people, according to the researchers.

At the least, "it provides another unexplored avenue for investigation" into obesity, said Catherine Kotz, an adjunct associate professor and nutrition specialist at the University of Minnesota who's familiar with the study findings.

While germs are generally considered to be villains, some bacteria in the body actually wear white hats. In the digestive system, they help break down food and serve other roles.

The study authors at Washington University School of Medicine in St. Louis wondered if the makeup of gut bacteria differed between lean and fat people. So they studied bacteria from the feces of 12 obese people over a year-long period while the subjects were on strict diets.

The researchers found that the obese study participants had fewer of the Bacteroidetes type of bacteria and more of the Firmicutes type than a group of lean people. The same researchers found in a related study that a similar germ makeup in mice appears to make their bodies better able to extract calories from food -- resulting in weight gain.

However, as the obese individuals continued to diet, their bacterial levels became more like those of the lean people.

Lead investigator Dr. Jeffrey Gordon, director of the university's Center for Genome Sciences, said these twin studies raise a number of questions. "Are some adults predisposed to obesity because they 'start out' with fewer Bacteroidetes and more Firmicutes in their guts?" he asked in a prepared statement. "Can features of a reduced Bacteroidetes-Firmicutes enriched microbial community become part of our definition of an obese state or a diagnostic marker for an increased risk for obesity? And can we intentionally manipulate our gut microbial communities in safe and beneficial ways to regulate energy balance?"

Kotz said the study, which is published in the Dec. 21 issue of Nature, appears to be well done.

Still, she said, "more work needs to be done to confirm this work and to determine whether gut bacterial can predispose one to obesity, or whether changing gut bacteria can in fact influence body weight. The current data indicates that gut bacteria may be associated with body weight but does not show that it contributes to the regulation of body weight."

More information

Learn more about bacteria from the University of California at Berkeley.