Gut bacteria: Genes influence the fit of your jeans

Our genetic makeup influences whether we are fat or thin by shaping which types of microbes thrive in our body, according to a Cornell-led study.

By studying pairs of twins, researchers identified the Christensenellaceae bacterial family, which is highly heritable and more common in lean people.

Furthermore, a member of this class of bacteria, Christensenellaceae minuta, protected against weight gain when transplanted into mice.
Twin girls walking on grass

The findings, published in November 2014 in the journal Cell, pave the way for personalized probiotic therapies that are optimized to reduce the risk of obesity-related diseases based on an person’s genetic makeup.

The connection between gut microbes and weight

“If you look across the population of gut bacteria and explain abundances, there is a host genetic component,” said Ruth Ley, associate professor of microbiology and the paper’s senior author. “Up until now there had been no direct evidence that anything in the human gut is under that kind of genetic influence.”

Genetic data that included 171 identical and 245 fraternal twins, whose genomes have been sequenced at King’s College in London and are stored in its “TwinsUK” registry, gave them the power to answer questions and rank which microbes in the human gut are heritable, Ley said.

Professor Tim Spector, Head of the Department of Twin Research and Genetic Epidemiology at King’s College London, said, “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.”

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With twins raised in the same households, “you can assume that environmental influences are going to be very similar to one another,” said Julia Goodrich, a graduate student and National Science Foundation Graduate Research Fellow in Ley’s lab and the paper’s first author. When Goodrich analyzed the microbe populations in the twins’ fecal samples, she found that identical twins, who have the same genetic makeup, had more similar gut microbiotas to each other than did fraternal twins, who share half the same genes.

“Up until now, variation in the abundances of gut microbes has been explained by diet, the environment, lifestyle, and health,” says senior study author Ruth Ley of Cornell University. “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.”

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