Body weight heavily influenced by gut microbes: Genes shape body weight by affecting gut microbes

Our genetic makeup influences whether we are fat or thin by shaping which types of microbes thrive in our body, according to a study by researchers at King's College London and Cornell University. By studying pairs of twins at King's Department of Twin Research, researchers identified a specific, little known bacterial family that is highly heritable and more common in individuals with low body weight. This microbe also protected against weight gain when transplanted into mice.

Picture showing different microbes found in gut

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, funded by National Institutes of Health (NIH), researchers sequenced the genes of microbes found in more than 1,000 fecal samples from 416 pairs of twins. The abundances of specific types of microbes were found to be more similar in identical twins, who share 100 per cent of their genes, than in non-identical twins, who share on average only half of the genes that vary between people. 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 a low body weight 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.

Picture showing comparison between treated and non treated mice.

 Several 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 micro biome represents an exciting new target for dietary changes and treatments aimed at combating obesity.

This is a crowd-sourcing experiment that allows anyone with an interest in their diet and health to have their personal microbes tested genetically using a simple postal kit and a small donation. 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.