Obesity affects nearly 900 million adults worldwide, and it is linked to conditions such as diabetes, high blood pressure, and heart disease. Now, new research suggests that changes in mouth bacteria in obesity are not just markers of poor health but may contribute to metabolic problems linked to obesity.

The findings, published in Cell Reports, point to new avenues for preventing and treating the condition.

Although genetics play a role, obesity is mainly driven by lifestyle changes, including reduced physical activity and diets rich in highly processed foods. The gut microbiota is known to influence obesity, and emerging evidence suggests that people with obesity have less diverse and more inflammatory oral bacteria. But it is unclear whether and how oral bacteria may affect whole-body metabolism.

So, Ahmed Shibl at New York University Abu Dhabi in the United Arab Emirates and his colleagues analyzed data from the UAE Healthy Future Study, a project designed to understand factors that contribute to heart and metabolic diseases among Emirati adults.

Microbiota differences

The researchers analyzed data from 669 participants aged 18 to 43, collecting mouthwash samples, health measurements such as body weight, blood pressure, and cholesterol, and detailed lifestyle information, including smoking and exercise habits. 

By analyzing mouth bacteria, the team found that obesity was associated with distinct bacterial communities, lower microbial diversity, and increased levels of microbes linked to inflammation.

The researchers also found that many microbial pathways involved in breaking down sugars and generating obesity-related compounds were more active in obese people than in healthy-weight people.

Therapeutic strategies 

Compared to healthy-weight individuals, those with obesity had higher levels of molecules that are known to promote inflammation, interfere with insulin signaling, increase hunger, and raise the risk of diabetes and fatty liver disease. At the same time, people with obesity showed reduced microbial pathways responsible for making essential B vitamins, which are important for healthy energy use.

Computer models combining oral bacteria, their metabolic functions, and saliva chemicals could better distinguish obese from healthy individuals compared with clinical measurements alone. 

These results indicate a potential role of mouth bacteria in obesity-related diseases, the authors say. The findings, they add, “also suggest opportunities for microbiome-based prevention and therapeutic strategies against obesity and underscore the importance of investigating the oral microbiome’s contributions to other complex diseases.”