Body weight affects your gut microbiota
Your body weight and genes influence the types of bacteria you have in your gut. In turn, this appears to affect the risk of developing conditions such as coeliac disease and haemorrhoids.
Gut microbiota – you have trillions of them. They affect digestion and nutrient absorption in your body. At the same time, they play a key role in your immune system, so it is important to take good care of them.
Kristian Hveem. Photo: NTNU
A new study now shows that body weight also affects gut microbiota.
“We demonstrate that there is a correlation between gut microbiota and body weight. We have also observed that having a high BMI is detrimental to gut microbiota,” said Professor Kristian Hveem from NTNU’s Department of Public Health and Nursing.
Body weight thus causes direct and adverse changes in gut microbiota composition, which in turn can lead to disease. However, this is also influenced by your genes.
The new findings have been published in Nature Genetics, and an international Nordic research group is behind the recent research article.
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12,662 participants from Trøndelag
Hveem previously headed the K.G. Jebsen Center for Genetic Epidemiology at NTNU. He also helped establish the HUNT Biobank and led it for 20 years. This biobank stores and contributes to new analyses of material from the large HUNT Study in Trøndelag, in which over 250,000 people have contributed health data.
In the HUNT4 survey, he organized the collection of stool samples from more than 13,000 participants. In 12,662 of these cases, researchers have conducted a detailed analysis of both bacteria and viruses found in the gut and examined how people’s genes influence their gut microbiota composition.
In total, the researchers used data from 28,000 people in various parts of the study.
Linked to coeliac disease and haemorrhoids
These bacteria, along with fungi, viruses and other microorganisms, constitute what is known as the gut microbiome, and taking care of it is important.
“Research shows that gut microbiota may also be linked to conditions such as coeliac disease and haemorrhoids,” explained Hveem.
Although the researchers have demonstrated a correlation between bacterial microbiota composition and various diseases, the underlying cause has yet to be determined.
Interaction between genes, body weight and disease
In other words, your gut microbiota alone do not determine whether you get sick or not. It is far more complicated than that.
“There is also an interaction between genetics, the composition of the gut microbiota and the risk of disease,” explained Hveem.
Your genes also influence the types of bacteria in your digestive system. With this study, the researchers have taken an important step forward.
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Linking specific genes to bacteria and function
“We can link specific genes to specific bacterial species found in an individual, and not just which genes and bacteria, but also what these bacteria do,” said Hveem.
Marta Riise Moksnes. Photo: Anne Line Bakken, NTNU
This is an important step forward that could prove useful for future research.
The article published in Nature Genetics is primarily a collaboration between the NTNU research group and Professor Claes Ohlsson at the University of Gothenburg. Kristian Hveem is a co-senior author.
The research has been largely funded by the Swedish Heart Lung Foundation, the Swedish Research Council, the European Research Council and the Kristian Gerhard Jebsen Foundation.
NTNU researcher Marta Moksnes is the lead author and a postdoctoral fellow at the University of Gothenburg. Other co-authors from NTNU are Eivind Coward, Ben Brumpton, Rebekka Hjort, Eivind Ness-Jensen and Guro Giskeødegård.
References:
Moksnes M.R. et al.; (2026); The HUNT study identifies host genetic factors reproducibly associated with human gut microbiota composition, Nature Genetics, DOI: 10.1038/s41588-026-02502-4
Dekkers K. et al. (2026); Genome-wide association analyses highlight the role of the intestinal molecular environment in human gut microbiota variation. Nature Genetics, DOI: 10.1038/s41588-026-02512-2
