Research into germs that travel through the human digestive tract shows that some may promote obesity while others might help prevent it.

Not only that, but those microbes may act differently in men versus women, the same study found.

“Our findings reveal how an imbalance in distinct bacterial groups are likely to play an important role in the onset and development of obesity, with considerable differences between the sexes," said study lead author Dr Paula Aranaz, from the Centre for Nutrition Research at the University of Navarra in Spain.

Her team is slated to present the findings in May at the European Congress on Obesity in Venice.

The researchers focused on an end product of human digestion: poop. They carefully analyzed the "metabolome" of stool samples from 251 female and 110 male adult volunteers, averaging 44 years of age.

The metabolome is the variety of metabolite molecules that form as gut bacteria break down food, the researchers explained in a meeting news release.

Aranaz' team also used genetic profiling to identify the various types of bacteria in the stool samples.

The participants ran the gamut in terms of weight — 65 were normal weight, 110 were overweight and 186 were deemed obese.

Certain microbial patterns emerged when it came to correlations between gut microbes and weight.

For example, folks who were obese tended to have lower gut levels of Christensenella minuta, a bacterium that's long been linked to healthy slimness.

After that, differences emerged based on a person's gender. Among men, higher levels of two bacterial species, Parabacteroides helcogenes and Campylobacter canadensis, appeared linked to piling on excess pounds.

Among women, higher amounts of three species — Prevotella micans, Prevotella brevis and Prevotella sacharolitica — were linked to obesity and overweight. That wasn't true for men, Aranaz' team noted.

Aranaz said the findings suggest that the distinct bacterial makeup of the gut can "influence the development of metabolic disease," including obesity.

The findings might pave the way to new ways of preventing or treating weight gain, she said. However, "interventions to help prevent an obesity-favorable microbiome may need to be different in men and women," she said.

Because the findings are being presented at a medical meeting, they should be considered preliminary until published in a peer-reviewed journal.