Obesity and Alzheimer's Cause Similar Brain Changes Linked to Cognitive Decline

by Liz Neporent
February 1, 2023 at 11:03 AM UTC

Obesity changes the brain in a very similar way to Alzheimer's.

Clinical Relevance: Weight control, especially in middle age, may be neuroprotective

  • A study by scientists at the Montreal Neurological Institute-Hospital of McGill University found similarities in the brain atrophy patterns caused by obesity and Alzheimer’s disease.
  • The study suggested that the cause of this brain thinning could be due to obesity-related inflammation, hormonal resistance or simply be a coincidence, and further research is needed to determine the exact mechanism.
  • Losing weight, or maintaining a healthy weight, in midlife could lower the risk of cognitive decline and dementia.

A new study offered some insight into why having obesity in midlife is a risk factor for brain atrophy and cognitive decline

Scientists at the Montreal Neurological Institute-Hospital of McGill University looked at the brain imaging data from over 1,300 patients to see if they could spot any similarities in atrophy patterns caused by either obesity or Alzheimer’s disease (AD.) Previous research has suggested a connection between obesity and AD-related changes in the brain including cerebrovascular damage and amyloid-β accumulation. But to date, no research had tried to make a direct comparison between the two conditions and what they do to the brain.

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Here’s what the investigation found: obesity brain maps and AD-brain maps were very similar in terms of thinning patterns, even when the AD subject sample was limited to lean individuals. Regions in the right temporal and left prefrontal cortex showed the most overlap in thinning but didn’t correlate very much when it came to the distribution of amyloid-β or tau protein, a long suspected marker of AD.

Cortical thinning could be a sign of neurodegeneration, said the authors. So their findings suggest that obesity may lead to the same type of neurodegeneration found in AD.

But why? There are any number of reasons, study authors said. 

One explanation is that obesity-related inflammation, hypertension or diabetes leads to changes in the brain that in turn trigger the brain changes responsible for AD. Another potential driver could be insulin and leptin resistance. Both hormones normally protect neurons from damage, but perhaps obesity somehow causes them to malfunction. Or, it could simply be a coincidence; the brain thinning attributed to obesity and AD may be unrelated with the correlation simply reflecting a higher occurrence of obesity in AD populations.

No matter which answer turns out to be correct, the authors said their findings build on previous literature pointing to obesity as a significant factor in AD “by showing that cortical thinning might be one of the potential risk mechanisms.” It’s already well established that obesity is a multisystem disease affecting the central nervous system as well as the respiratory, gastrointestinal, and cardiovascular systems.

And, the authors said, their research suggests that keeping the waistline under control, particularly in middle age, should be a priority for better brain health. Further, losing excess weight could slow cognitive decline in aging and lower risk for AD.

“Our results highlight the importance of decreasing weight in obese and overweight individuals in mid-life, to decrease the subsequent risk of neurodegeneration and dementia,” Filip Morys, the study’s first author, said in a news release. 

No one would argue with this idea, but as any dieter will tell you, the struggle is real. Processed foods high in sugar, simple starches, and fat can really pile on the pounds and alter the brain in ways similar to other addictions like smoking and drinking, the evidence suggests.

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