Genetics could determine what type of microbes live in our gut, influencing whether we are fat or thin.
Researchers looked at a rarely studied bacterial family that tends to be inherited and is more common in thinner people and found it protected mice against weight gain, King's College London reported.
In the past researchers have found both genetic variation and gut microbes have an effect on body weight, but the link between all three of these factors has not been looked at closely.
To make their finding researchers sequenced the genomes of microbes found in more than 1,000 fecal samples from 416 pairs of twins. They found the type of bacteria whose abundance was most heavily influenced by genetics was a family called "Christensenellaceae," which are more abundant in individuals with lower body weight.
The researchers then treated mice with the microbe and found they gained less weight than untreated mice, suggesting the bacteria could help prevent or reduce obesity.
'Our findings show that specific groups of microbes living in our gut could be protective against obesity - and that their abundance is influenced by our genes. The human microbiome represents an exciting new target for dietary changes and treatments aimed at combating obesity," said Professor Tim Spector, Head of the Department of Twin Research and Genetic Epidemiology at King's College London.
Twins are helpful in finding these links, but in the future the researchers hope to look at the prevalence of this bacteria in larger populations.
"Up until now, variation in the abundances of gut microbes has been explained by diet, the environment, lifestyle, and health. This is the first study to firmly establish that certain types of gut microbes are heritable -- that their variation across a population is in part due to host genotype variation, not just environmental influences. These results will also help us find new predictors of disease and aid prevention," said Ruth Ley, Associate Professor at Cornell University.
The findings were published in a recent edition of the journal Cell.
