Our genetic make-up influences the type of bacteria that live in our gut, which in turn may influence how likely we are to be overweight, a twin study has found.
Researchers from Cornell University in the USA examined bacteria in over 1,000 faecal samples taken from 416 sets of twins. They found that levels of some bacteria were more similar in identical twins (who share all their genes) than in non-identical twins.
'Our primary goal was to establish, once and for all, whether there was an effect of host genotype on the composition of the gut microbiome,' said Dr Ruth Ley, associate professor at Cornell and senior study author.
Twins raised in the same households have very similar environments, so differences in bacteria seen in the study are likely to be explained by genetic factors. Study participants were from the TwinsUK registry and had their genomes sequenced at King's College London.
Bacteria from the family Christensenellaceae were the most strongly heritable and higher levels of these microbes were found in leaner people, leading to the hypothesis that Christensenellaceae levels can influence body weight.
Professor Tim Spector, of the Department of Twin Research at King's College who co-authored the study, told New Scientist: 'Everyone has a small amount of it (Christensenella), around one percent, but some people have as much as 10 percent. We think the more you have, the more protected you are against obesity.'
To explore this theory, the researchers exposed mice without gut bacteria to faecal samples from lean and obese people. Mice exposed to samples richer in Christensenella gained less weight than mice receiving samples with little of the bacteria.
Although findings in mice are still preliminary, the study may yet have implications for treatment of obesity. Dr Ley told BBC News: 'Once we have found out how it works in mice, if it seems that we can apply that to humans we can look into developing this as a probiotic to regulate weight.'
The research was published in the journal Cell.