The new study published in Communications Medicine explored whether body mass index (BMI) acts as a shared biological factor behind multimorbidity, the presence of two or more long-term conditions in one person.
The team analyzed genetic data related to 71 chronic diseases using large research databases, including the UK Biobank and FinnGen.
By applying methods such as Mendelian randomization, they assessed whether higher BMI plays a causal role in linking diseases, rather than merely being associated with them.
When BMI explains disease clusters
In total, 2,485 possible disease pairs were examined. In 1,362 pairs, the genetic overlap between conditions weakened after accounting for BMI.
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In 161 pairs, BMI appeared to fully explain the shared genetic risk.
These included combinations involving chronic kidney disease, osteoarthritis and type 2 diabetes.
The researchers estimated that reducing BMI by one standard deviation, roughly 4.5 BMI units, could prevent about 16 cases per 1,000 people of co-occurring chronic kidney disease and osteoarthritis, and 9 cases per 1,000 of type 2 diabetes and osteoarthritis.
These projections reflect long-term genetic associations, not short-term weight loss effects.
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Not the whole story
BMI did not explain genetic overlap in 1,123 disease pairs, indicating that other biological mechanisms contribute to multimorbidity.
In some instances, such as osteoporosis, lower BMI was associated with higher risk.
The authors note that BMI is a broad measure of body fat and that the analysis primarily included individuals of European ancestry.
Still, the findings suggest obesity may serve as a shared driver behind certain combinations of chronic disease.
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Source: News-medical, and Communications Medicine.
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