Predicting Obesity in Children: The Gut Bacteria Obesity Connection

June 6, 2023

A bacterial imbalance in the microbiome has already been linked to obesity in adolescents and adults but it may now be possible to determine the risk of obesity earlier. It turns out that early indicators of a child’s risk of becoming obese can be found by swabbing their mouth for those imbalances.

This research could be used to provide parents with the foresight they need to combat childhood obesity. So what is this bacteria, what’s causing it and how can you reduce your child’s risk of obesity? We outline it in the following sections.

  • What bacteria is causing obesity?
  • What can I do to the reduce risk?
  • How to treat microbiome imbalances
  • More information of the microbiome and obesity

Let’s first discuss which bacteria are causing this increase risk in obesity.

What bacteria is causing obesity?

A lack of microbial diversity is associated with those who are or are at risk of becoming obese. Most notably a ratio imbalance between Firmicutes and Bacteroidetes has been seen in those with an increased risk of obesity. Higher rates of Firmicutes have also been consistently found in the guts of those who are already obese.

Firmicutes, Bacteroidetes and obesity

Researchers have found specifically that a greater ratio of Firmicutes to Bacteroidetes in the human microbiome increases one's risk of becoming obese. This association has also been made to those who remain obese - in a study from the Mayo Clinic, results showed that those with a higher abundance of Dialister (a Firmicutes bacteria) had a harder time successfully losing weight than those with lower levels of the bacteria.

Predicting obesity in babies

Until recently this Firmicutes to Bacteroidetes ratio was thought untraceable in children below the age of two who had incomplete gut microbiomes. New research has uncovered that this imbalance can be found earlier on, that is before the age of two, in the mouth microbiome.

As of yet the reason for this unbalanced ratio is unknown: it could be associated with a genetic predisposition, environmental factors, or diet. It is likely some combination but the exact source has not yet been adequately studied.

What can I do to reduce the risk?

Though there is no knowing how to stop this imbalance in infants, there are a few factors that put children at an even higher risk for developing obesity. Certain environmental factors in the early stages of microbiome development can have long standing consequences. So, what can be done to minimize your child’s risk?

Two factors that have been found are heavy use of household disinfectants and cleaners and use of antibiotics in young age.


A University of Alberta study showed that household disinfectants have been associated with higher levels of firmicutes in the gut microbiome of children. Specifically, Lachnospiraceae (a member of the Firmicutes family), a bacteria known for its increasing risk of obesity. Try substituting natural cleaners for harsh chemical cleaners as much as you can.


Antibiotics can be life saving drugs and should not be refused if needed, but overuse of them is a problematic trend. Though the correlation has been made mostly in animal models for the use of antibiotics and its effect on obesity, there is good reason to believe that it similarly effects and harms metabolic processes in humans. In short, antibiotics harm microbial diversity and lack of microbial diversity puts one at a greater risk of becoming obese. What needs to be done now is research into the exact mechanisms that make antibiotics so harmful to the human microbiome.

How to treat the imbalance

If you have this imbalance and are already grown up, or your child is already past the age of full microbiome development (age three) there are behaviours you can participate in that may help your microbiome diversity or help reverse some of these imbalances that set in while you were young.


There haven’t been any wholly conclusive studies on what specifically about diet affects the microbiome but it is known that a plant rich diet is beneficial for the microbiome, while a western style diet, with high

sugar and high fat has been associated with dysbiosis of the microbiome. The safest bet is to eat plenty of whole fruits and vegetables and to stay away from processed foods, especially processed sugar.


Exercise is not just good for your cardiovascular system, etc, it turns out it can also be beneficial for your microbiome. Exercise has been found to help gut flora flourish and has the potential balance the Firmicutes and Bacteroidetes ratio within the gut. Remember that F:B ratio is the marker that increases risk of obesity.  

Fecal Transplants

Fecal Microbiota Transplantation (FMT) is currently being explored as a therapy for adults and teens who are clinically obese. Though results have not yet been published, the concept holds promise. FMT itself may not be the exact answer, but the exploration of the microbiome and how we can manipulate it may one day provide an effective treatment for those who have trouble losing unhealthy amounts of weight.

More information on the microbiome and obesity

How Some Pesky Bacteria In Your Gut May Be Messing Up Your Weight Loss Diet

Is your microbiome stopping you from losing unhealthy weight? Read more about the Mayo Clinic study into gut bacteria and weight loss trends.

FMT Treatments and Therapies

If you are interested in learning more about FMT (as mentioned in this article) check out some of these pieces on all the conditions FMT is being used to treat.

Household disinfectants could be making kids overweight, study says

Read more about the effect household disinfectants are having on obesity risk in children. Are you cleaning your microbiome into oblivion?