Microbes living in our mouths could hold the key to obesity prevention - medicalxpress

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Scientists may have found a new way to spot early signs of obesity, which could lead to novel prevention strategies. A study published in the journal Cell Reports has discovered that people living with obesity have a distinct set of microbes in their mouths compared to people at a healthy weight.

Obesity is a global health crisis, a chronic relapsing disease where people have a BMI (body mass index) greater than or equal to 30. According to the World Health Organization, around 890 million people are living with obesity (data from 2022), while 2.5 billion adults are overweight (a BMI greater than or equal to 25).

Oral microbes

There are many known causes for weight gain, such as diet, lifestyle and genetics. The gut microbiome, the community of microbes that live in our digestive tract, also affects weight. But little is known about the possible link between obesity and the microbes living inside our mouths, which is the second-largest microbial ecosystem in the body. 

Graphical abstract. Credit: Cell Reports (2026). DOI: 10.1016/j.celrep.2025.116819

To see where oral microbes may fit into the picture, scientists at New York University Abu Dhabi in the United Arab Emirates sequenced the microbial DNA in saliva samples from 628 Emirati adults, 97 of whom had obesity. The results were compared with those of 95 healthy-weight participants who were matched for age, lifestyle and oral health habits.

Problematic bacteria

The comparison revealed that individuals with obesity have more bacteria, such as Streptococcus parasanguinis, that trigger inflammation. There was also a higher number of microbes that produce lactate. High levels of lactate are associated with an increased risk of type 2 diabetes and poor metabolism.

Beyond the types of bacteria, the researchers found 94 differences in how these microbes function. For example, in the group with obesity, the bacteria were more active in breaking down sugars and proteins that can cause health problems. These metabolic differences also led to higher levels of chemicals called uridine and uracil, which can act as signals that increase a person's appetite. The team also found these bacteria were less capable of producing essential nutrients the body needs to stay healthy.

Obesity prevention

At the moment, the scientists do not know whether the microbial differences are a cause or an effect of obesity. Either way, their presence could be a powerful tool for early detection, as they note in their paper: "These findings reveal mechanistic oral microbiome-metabolite shifts, highlighting oral microbiome-host interactions as novel targets for obesity prevention and intervention."

That could mean that in the future, a simple mouthwash test could be used to identify risks before they lead to weight gain. If the microbes are a cause, new treatments could be developed to improve the oral ecosystem and prevent obesity. 

© 2026 Science X Network

by Paul Arnold, Medical Xpress

edited by Gaby Clark, reviewed by Robert Egan 

Source: Microbes living in our mouths could hold the key to obesity prevention