Your Child's Mouth Could Reveal Their Obesity Risk

Scientists believe the bacteria that live in a toddler's mouth could provide clues as to whether they will become obese.

Existing research suggests the microbes inhabiting the guts and mouths of obese adults differ to those without the condition, but less is known about this pattern in children.

So biologists at Pennsylvania State University set out to investigate what a child's microbiota could say about their weight.

Microbiota is the term used to describe the microbes—including the bacteria, fungi and viruses—which live in and on our bodies. What we eat can affect the makeup of this population of bugs which outnumber our own cells 10 to one.

The bugs which populate a child's mouth could indicate their risk of becoming obese, according to research. Getty Images

The Penn State study published in the journal Scientific Reports is the latest to uncover the important role these microbes play in our physical and mental health.

Researchers collected the gut and oral microbiota of 226 two-year-old children by swabbing their mouths and taking stool samples. They also took mouth swabs from the infants' mothers. The participants' RNA (a molecule which affects how genes are expressed) was then sequenced.

The children were taking part in the Insight trial at Penn State, which explores how a child's biology and socioeconomic status affects their chance of becoming obese.

Children with rapid infant weight gain—a growth pattern which is a key indicator of whether a baby will become obese—were found to have a less diverse range of microbes in their mouths. They also had a higher ratio of Firmicutes to Bacteroidetes bacteria in their oral microbiota than the others. These findings didn't relate to the gut, however, indicating the children's bug population was still developing.

These findings mirrored previous research into obese adults and teenagers, showing similar trends in bugs in their guts, the authors said.

Around 93.3 million adults in the U.S. are obese, according to the latest official figures from 2015 to 2016. Getty Images

Dr. Sarah Craig, an author of the study and postdoctoral scholar in biology at Penn State, explained: "A healthy person usually has a lot of different bacteria within their gut microbiota. This high diversity helps protect against inflammation or harmful bacteria and is important for the stability of digestion in the face of changes in diet or environment.

"There's also a certain balance of these two common bacteria groups, Firmicutes and Bacteroidetes, that tends to work best under normal healthy conditions, and disruptions to that balance could lead to dysregulation in digestion."

Craig told Newsweek the study was limited by having one time point to study the microbiota. "This is a dynamic community, so we are really only seeing a snapshot of what is happening," she said.

Next, the researchers hope to replicate their results in a more diverse population of children outside of Pennsylvania, and potentially create a test to pick up kids who are at the greatest risk of becoming obese.

Craig told Newsweek: "There are many factors that contribute to obesity and obesity prevention—along with a healthy diet and physical activity, biological factors, such as the microbiota for instance, could also be a potentially important consideration."

An oral test for obesity isn't on the horizon, she said.

"We're really in the early stages of understanding how these microbes are influencing health. And importantly, we also do not know the causal relationship; or more simply put, are the microbes influencing weight/health or is health influencing the microbes, or is it both ways? But hopefully with this study and our ongoing study we will be closer to a fuller understanding."

The study was published days after a separate paper in the Canadian Medical Association Journal showed children who lived in households where disinfectants were used at least once a week had a higher BMI by age three years old compared with children who were exposed to such products less regularly. Eco-friendly products, however, appeared to have the inverse effect.

The researchers arrived at their findings by studying the gut flora of 757 babies aged between three to four months old.

This article has been updated with comment from Dr. Sarah J.C. Craig.