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Obesity is associated with an increase in dementia risk and researchers can now see that it speeds up the development of Alzheimer’s in particular
Rebecca WhittakerTuesday 02 December 2025 10:03 GMTComments
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Blood tests have indicated that obesity could speed up the development of Alzheimer’s disease, a study has revealed.
There are currently estimated to be 982,000 people with dementia in the UK and obesity is a known risk factor.
In fact, obesity between the ages of 35 and 65 can increase dementia risk in later life by about a third, according to the Alzheimer’s Society. This could be because obesity increases the risk of high blood pressure and type 2 diabetes - which both contribute to a risk of dementia.
But US researchers have shown for the first time a link between obesity and Alzheimer’s disease using blood tests.
Signs of Alzheimer’s disease shown in blood biomarkers, increased up to 95 per cent faster in individuals with obesity than in non-obese individuals, according to a new study. It is set to be presented at the annual meeting of the Radiological Society of North America (RSNA).
Obesity can speed up the development of Alzheimer’s disease, study finds (stock image) (Getty/iStock)As part of the study researchers looked at five years worth of data from 407 participants, which included brain scans and blood samples.
Researchers focused on a blood test that measures a protein called p-tau217. High levels of this protein are a strong indicator of amyloid plaques - the sticky protein clumps that are a hallmark of Alzheimer's disease.
Analysis of blood samples and brain scans showed a higher BMI was associated with lower blood biomarkers (BBMs) and reduced amyloid plaques - however this was not the case in the long-term data.
“We believe the reduced BBMs in obese individuals was due to dilution from the higher blood volume,” said study lead author Soheil Mohammadi, postdoctoral research associate at Mallinckrodt Institute of Radiology.
Dr Mohammadi said just by looking at these results you could be “fooled” into thinking that the people with obesity had a lower risk of Alzheimer’s disease.
But when researchers studied the participants over time, those who were obese experienced significantly faster rates of amyloid plaques developing compared to those who were a healthy weight.
Participants with obesity had a 29 per cent to 95 per cent faster rate of increase in plasma pTau217 ratio levels - suggesting the presence of Alzheimer’s disease.
Dr Cyrus Raji, senior author of the study, said their analysis demonstrated that the blood tests were more sensitive than the brain scans in capturing the impact of obesity on Alzheimer’s development.
He believes longitudinal assessments with blood biomarkers with brain health imaging will become the norm for monitoring treatment and anti-amyloid drugs.
“This is such profound science to follow right now because we have drugs that can treat obesity quite powerfully, which means we could track the effect of weight loss drugs on Alzheimer’s biomarkers in future studies,” he said.
“It’s marvellous that we have these blood biomarkers to track the molecular pathology of Alzheimer’s disease, and MRI scans to track additional evidence of brain degeneration and response to various treatments. This work is foundational for future studies and treatment trials.”
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