Oral microbiome differences linked to obesity in new study

Researchers have identified distinct differences in the oral microbiome of people living with obesity, raising the possibility that microbes in the mouth could be used to help detect obesity risk at an early stage.

The findings, published in Cell Reports, suggest that changes in oral bacteria may offer new opportunities for obesity prevention and intervention strategies.

Obesity is recognised as a chronic, relapsing disease and is defined by a body mass index of 30 or above. It represents a major global public health challenge. According to the World Health Organization, approximately 890 million people worldwide were living with obesity in 2022, while around 2.5 billion adults were classified as overweight, with a body mass index of 25 or above.

While diet, physical activity and genetic factors are well-established contributors to weight gain, increasing attention has focused on the role of the microbiome in metabolic health. Most research to date has examined the gut microbiome. However, the oral cavity represents the second-largest microbial ecosystem in the human body, and its role in obesity has been relatively unexplored.

To investigate this, scientists from New York University Abu Dhabi analysed saliva samples from 628 Emirati adults, including 97 individuals living with obesity. These were compared with samples from 95 healthy-weight participants matched for age, lifestyle factors and oral health behaviours.

The analysis showed that people living with obesity had higher levels of bacteria associated with inflammation, including Streptococcus Parasanguinis. They also had increased numbers of lactate-producing microbes. Elevated lactate levels have previously been linked to impaired metabolism and a higher risk of type 2 diabetes.

In addition to differences in bacterial species, the researchers identified 94 functional differences in microbial activity between the two groups. In participants living with obesity, oral microbes showed increased activity in breaking down sugars and proteins linked to adverse metabolic effects.

These functional changes were associated with higher concentrations of uridine and uracil, compounds that may act as signalling molecules influencing appetite regulation. The study also found reduced capacity among these microbes to produce certain nutrients required for optimal health.

The researchers caution that it is not yet clear whether these microbial changes are a cause or a consequence of obesity. However, they argue that the findings highlight the oral microbiome as a potential target for early risk identification.

If confirmed in further studies, the findings could lead to the development of simple screening tools, such as saliva or mouthwash-based tests, to identify individuals at higher risk of developing obesity before significant weight gain occurs.

In the longer term, targeted therapies aimed at modifying the oral microbiome may offer a new approach to supporting obesity prevention by restoring a healthier microbial balance in the mouth.