Healthy living

Early Alzheimer's may be linked to low BMI

Early Alzheimer s may be linked to low BMI May indicate changes to metabolism

People in the earliest stages of Alzheimer's disease are more likely to have a lower body mass index, a study suggests.

Scientists from the University of Kansas say the findings suggest that changes in the brain which occur in the early stages of Alzheimer's may be linked to a change in body metabolism caused by the disease.

The researchers looked for early changes in the brain associated with Alzheimer's using an advanced brain imaging technique in a study involving 506 people. Samples of cerebrospinal fluid were also tested for two biomarkers which can be present before the first symptoms of Alzheimer's appear.

The study participants included people without memory problems, people with mild cognitive impairment and people with Alzheimer's disease. People with mild cognitive impairment experience mild memory problems, but not to an extent that interferes with their daily life.

The study found that people who had Alzheimer's biomarkers and signs of amyloid plaques in their brains were more likely to have a body mass index below 25.

Among those with mild cognitive impairment, 85 per cent of the people with a BMI below 25 had signs of beta-amyloid in their brains compared with 48 per cent of those with mild cognitive impairment who were overweight.

Past studies have shown that being overweight in middle-age can actually increase your risk of developing Alzheimer's, but those who are overweight later on in life may have a lower risk of disease, known as the "obesity paradox."

However, the scientists do not recommend putting on weight to lower your risk of disease. A low BMI may be a result of the disease, not the cause of it.

Dr Anne Corbett, research manager at the Alzheimer's Society, said: "As yet it is unclear whether a low BMI is actually part of Alzheimer's, or a side effect caused by the disease.

"Although this study shows a link between it and changes in the brain common to Alzheimer's, there was no association between BMI and symptoms of the disease such as memory loss.

"More work is needed before we can say if these findings could be used to develop better ways of diagnosing the early stages of the condition.

"What we do know is that living well will reduce your risk of developing Alzheimer's disease. Alzheimer's Society recommends people eat healthily and exercise regularly."

The findings are published in the journal Neurology.

This article was published on Tue 22 November 2011

Image © Karen Roach -

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