Individuals who lack key species of so-called "good" bacteria in their intestines are more prone to obesity and associated diseases such as diabetes, heart and cholesterol problems, according to research published Wednesday.
The findings may hold new clues to help tackle the world's obesity epidemic, which is predicted to affect more than 700 million people in 2015, a rise of 300 million in a decade, its authors said.
An international team of researchers compared the intestinal germs found in 169 obese Danes and 123 non-obese counterparts.
"We were able to distinguish between two groups based on their intestinal flora -- people with a large richness of bacterial species in their intestines and people with a few less bacterial species," said Jeroen Raes of the Flemish Biotechnology Institute (VIB) in Brussels.
Twenty-three percent of the sample had "low bacterial richness."
They turned out to be more likely to be obese -- but not exclusively so -- and to develop obesity-linked diseases.
The snapshot showed that the "high richness" group had on average 580,000 different genes in their intestinal bacteria.
Among the "low richness" group, there were just 360,000 different genes.
Six bacterial species appear to play the key role in promoting this diversity.
Further research is needed to develop these early-stage discoveries and see if they apply to other races and populations.
The hope is to develop "specific bacterial markers" to identify people at risk and even bacterial treatments to prevent weight gain, said Stanislas Dusko Ehrlich of France's National Institute for Agricultural Research (INRA), who coordinated the two studies published in the journal Nature.