When they included the microbiome, along with age, gender and genetics in looking at BMI and lipids, the combined contribution explain 26% of the differences in HDL (without the microbial information, the other factors explained about 19% to 20% of the variation among people).

Intestinal microbiomes might help determine not only body fat levels, but also blood concentrations of high-density lipoprotein (HDL) cholesterol and triglycerides, according to a study published online September 10 in Circulation Research.

Researchers from the University Medical Center Groningen in the Netherlands used “next generation” deep sequencing technology to study the association between gut microbes and blood lipid levels. The study authors said they were surprised to find that gut microbes had little to do with low-density lipoproteins (LDL) – the so-called bad cholesterol – or total cholesterol levels.

However, like obesity, the gut’s microbiome is complex, as diet alone isn’t the only thing that affects it. It can also react to the external environment as bacteria can differ from one place to another.

The participants additionally completed questionnaires about their diets, lifestyle habits, medical histories and the medications they were taking.

According to a report from Time, a new study has shown that the bacteria living in our guts have more to do with regulating metabolism than previously thought.

Overall, the researchers found 34 types of bacteria that were associated with people’s triglycerides and HDL levels, and with body mass index (BMI) – a measure of weight in relation to height.

Nutritionist Lyndi Polovnik told HuffPost Australia that your gut health affects not only your heart but all aspects of your health, from anxiety to depression to bowel cancer.

The researchers then suggested increasing the diversity of the gut flora in order to effectively control the weight-related factors, such as BMI and cholesterol levels.

Some researchers have referred to the bacterial community in the human gut as an “extra organ” in the body because of its important influence on a person’s health. “We can intervene with bacterial populations in the future”, says Fu, “because the microbiome can be targeted for treatment with probiotics or medicine”.

Scientists can probably also call gut bacteria “the heart in the gut”, Fu said.