LONDON  - Scientists in Britain have found a new link between the diversity of bacteria in human poo - the human fecal microbiome - and levels of harmful types of body fat.

In research that may help explain why excessive weight problems and obesity tend to run in families, the scientists said high levels of visceral fat - which is linked to risks of chronic disease - were linked to having a relatively small range of bacteria in faeces.

People with a high diversity of bacteria in their feces had lower levels of visceral fat, according to the study published on Monday in the journal Genome Biology.

Visceral fat is harmful because it sits around important organs like the liver, pancreas and intestines. It is linked to higher risks of diabetes and heart disease.

The scientists used data from stool samples from 1,313 twins already involved in a large research project called TwinsUK.

Extracting DNA information about fecal microbes from the samples, they then compared that to six measures of obesity, including body mass index, visceral and other fat levels, and upper to lower body fat ratios. They found the strongest links with visceral fat.

Michelle Beaumont, who led the work at King's College London, said it showed "a clear link between bacterial diversity in feces and markers of obesity and cardiovascular risk."

But she cautioned that since this was an observational study, it could not give any causal mechanisms for how gut and fecal bacteria might affect fat.

Jordana Bell, also from King's twin research department, said more studies were needed to understand precisely how gut microbes influence human health and to explore possible new ways of preventing obesity.

Further research would also help in investigating a possible role for procedures like faecal transplants - a treatment currently used in patients with an infection called C.difficile colitis which replaces their unhealthy fecal microbiome with a healthy one from a donor.