Our genetic makeup influences whether we are fat or thin by shaping which types of microbes thrive in our body, according to a British study published Thursday in the scientific journal Cell.

In a study involving twins at the Department of Twin Research at King's College London (KCL), researchers identified a specific bacterial family, which is highly heritable and more common in individuals with low body weight.

Previous research has linked both genetic variation and the composition of gut microbes to metabolic disease and obesity. Despite these shared effects, the relationship between human genetic variation and the diversity of gut microbes was presumed to be negligible.

In the study, researchers sequenced the genes of microbes found in more than 1,000 fecal samples from 416 sets of twins. The abundances of specific types of microbes were found to be more similar in identical twins, who share 100 percent of their genes, than in fraternal twins, who share only half of the same genes. These findings demonstrate that genes influence the composition of gut microbes.

The type of bacteria whose abundance was most heavily influenced by host genetics was a recently identified family called "Christensenellaceae." Members of this health-promoting bacterial family were more abundant in individuals with low body weights than in obese individuals.

Moreover, mice that were treated with this microbe gained less weight than untreated mice, suggesting that increasing the amounts of this microbe may help to prevent or reduce obesity.

According to researchers, their results could pave the way for personalized probiotic therapies that are optimized to reduce the risk of obesity-related diseases based on an individual's genetic make-up.