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

Body sizes (stock image). New research shows that our genetic makeup influences whether we are fat or thin by shaping which types of microbes thrive in our body. Credit: © olly / Fotolia

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.

The results, published today in the journal Cell, could pave the way for personalised probiotic therapies that are optimised to reduce the risk of obesity-related diseases based on an individual's genetic make-up.

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.

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.

'Twins have been incredibly valuable in uncovering these links -- but we now want to promote the use of microbiome testing more widely in the UK through the British Gut Project. 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 via our website (www.britishgut.org). We want thousands to join up so we can continue to make major discoveries about the links between our gut and our health.'

Ruth Ley, Associate Professor at Cornell University in the United States, said: '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.'

Source: King's College London

Moderate consumption of sugary drinks has little impact on adolescents' metabolic health

Sugar-sweetened beverages, such as soft drinks, are the largest source of added sugar in the diets of adolescents in the United States. Credit: Image courtesy of University of Missouri-Columbia

Sugar-sweetened beverages are the largest source of added sugar in the diets of adolescents in the United States, and young adults ages 15-20 consume more of these drinks than any other age group, according to the Centers for Disease Control and Prevention. Adolescent obesity rates, which have quadrupled over the past thirty years, led to widespread scrutiny of added dietary sugars, especially those found in carbonated beverages. Now, MU researchers have found that short-term, moderate consumption of high-fructose and high-glucose beverages has little impact on the metabolic health of weight-stable, physically active adolescents.

"These beverages may not be as unhealthy for adolescents as previously thought, provided that kids stay active," said Jill Kanaley, professor and associate chair in the MU Department of Nutrition and Exercise Physiology. "That physical activity component is really critical in protecting against some of the negative effects of drinking large amounts of sugar-sweetened drinks demonstrated in previous studies."

Kanaley's study measured several aspects of metabolic health, including insulin sensitivity and cholesterol levels, after participants had consumed moderate amounts of either high-glucose or high-fructose beverages every day for two weeks. The high-glucose drink contained 50 grams of glucose and 15 grams of fructose; the high-fructose drink contained 50 grams of fructose and 15 grams of glucose. In comparison, two 12-ounce cans of white soda contain about 50 grams of fructose, although the amount of sugar found in soft drinks varies by brand and type. The researchers used armbands with electronic sensors to monitor physical activity of the participants, all of whom were healthy male and female adolescents ages 15-20.

Although some research has shown that consuming sugary drinks can have detrimental metabolic effects, Kanaley said that the results of these studies have been inconsistent. Previous research often has excluded adolescents and did not measure participants' levels of physical activity. In one of her previous studies, which recently was published in Medicine in Science and Sports, Kanaley found that increased physical activity diminished negative effects associated with high-fructose diets.

"Many parents of adolescents worry about their children's consumption of sweetened beverages," Kanaley said. "I certainly would recommend that they work to reduce their children's intake of sugary drinks, but it also is important for kids to remain active, especially if they are drinking a lot of sugary beverages. In our study, the female adolescents averaged around 8,000 steps per day, and the males averaged about 10,000 steps per day. 

These children weren't athletes, but they had active lifestyles."

Kanaley's article was published in the American Journal of Clinical Nutrition.

Source: University of Missouri-Columbia