The findings, outlined in the journal Genome Biology, strongly suggest obesity is genetically influenced as heritable bacteria were found in the faecal microbiome.
The College’s research adds to mounting evidence that gut bacteria has a larger say in weight gain than previously thought.
Although obesity is the recognised global health concern, the build-up of abdominal fat has been identified as the single risk factor for cardiovascular disease and type 2 diabetes.
Quite where gut microbes’ role comes into play is still unclear but a number of theories have been suggested, including alterations in energy harvest from food and an increase in inflammatory microbe populations.
Analysis of twin poo
Researchers selected 1,313 sets of twins from the TwinsUK cohort that looked at stool samples and the DNA information about faecal microbes.
Six measures of obesity were compared, with BMI and upper to lower body fat ratios included. The strongest relationships concerned the levels of visceral abdominal fat.
The findings were further scrutinised using BMI as a measure of obesity in two more population based groups and another TwinsUK dataset.
“This study has shown a clear link between bacterial diversity in faeces and markers of obesity and cardiovascular risk, particularly for visceral fat,” said Dr Michelle Beaumont, the study’s lead author and research associate at the Department of Twin Research and Genetic Epidemiology at King’s.
“However, as this was an observational study we cannot say precisely how communities of bacteria in the gut might influence the storage of fat in the body, or whether a different mechanism is involved in weight gain.”
Previous studies have explored the heritability of the microbiome. One study found that twins had more similar microbiomes than marital partners or unrelated individuals.
Other studies have demonstrated that the heritable properties of the human faecal microbiome are strongly linked with visceral fat.
Altered microbial metabolism
In its concluding remarks, the study highlighted the extent in which microbial metabolism was altered in obese individuals.
The study believed that a low diversity of faecal bacteria could result in high levels of gut microbes that specialise in converting carbohydrates into fat.
“We see a strong positive association between visceral fat and glyoxylate and dicarboxylate metabolism,” the study commented
The glyoxylate cycle is a pathway that allows the metabolism of fatty-acids into glucose, contributing to insulin resistance where there is an excess of fatty acids.
More recently glyoxylate has been highlighted as a biomarker of type II diabetes, even by as much as three years prior to diagnosis of diabetes.
“There is a growing body of evidence to suggest that gut bacteria may play a role in obesity, and a number of studies are now exploring this in more detail,” said senior author, Dr Jordana Bell, from the Department of Twin Research and Genetic Epidemiology.
“Further scientific investigation is needed to understand how precisely our gut microbes can influence human health, and if interventions such as faecal transplants can have safe, beneficial, and effective impacts on this process.”
Source: Genome Biology
Published online ahead of print, DOI: 10.1186/s13059-016-1052-7
“Heritable components of the human fecal microbiome are associated with visceral fat.”
Authors: Michelle Beaumont et al.