- According to new research published in the Journal of Alzheimer’s Disease, a higher BMI means less blood flow to your brain, which means a higher risk of dementia—especially Alzheimer’s disease.
- However, BMI itself isn’t a measure of your 'health,' but rather a measure of your size.
- The key takeaway is staying fit is key to keeping your brain healthy in the long term.
Staying fit and maintaining your weight have been highlighted many times for the benefits those bring to your entire body—such as warding off cancer or death related to cardiovascular events—but a new study suggests keeping a stable weight can impact your brain health as well.
In research published in the Journal of Alzheimer’s Disease, scientists analysed over 35,000 functional brain scans from more than 17,000 individuals, looking at blood flow and brain activity, and comparing them based on participants’ body weight. Also assessed were differences in brain activity while people were at rest versus performing a task that required concentration.
Although the mean age of the people studied was 40, the scans encompassed an age range of 18 to 94, and included both men and women. Weight was determined using body mass index (BMI), which groups individuals into categories of underweight, normal weight, overweight, obese, and morbidly obese.
The researchers found that as BMI increased, blood flow to the brain tended to be lower, both during rest and concentration. This is significant because the less blood that goes to your brain, the higher your risk of dementia is—especially Alzheimer’s disease. Additionally, a decreased supply of blood to your brain has been associated with other conditions such as ADHD, depression, bipolar disorder, and schizophrenia.
Brain areas that are particularly vulnerable to Alzheimer’s seemed to be the most affected, Daniel Amen, M.D., the study’s lead author and founder of Amen Clinics, told Runner’s World.
Generally speaking, it’s true that the higher your BMI is, the higher your risk is of developing health conditions linked with being overweight—such as diabetes, high blood pressure, and high cholesterol. However, it’s worth noting that BMI itself is not measuring your 'health,' according to Harvard Medical School; rather, BMI is a measure of your size.
'It’s possible to be in the "healthy weight" range and have an unhealthful lifestyle,' Runner’s World previously reported. 'It’s possible to be heavily muscled and have relatively little body fat, but still have a BMI in the "overweight" range.'
Regardless, the takeaway, according to Amen, is that staying fit is key to keeping your brain healthy in the long term. In terms of the reason why, Amen said that fat cells increase inflammation—which has been shown to damage all organs, including the brain.
'Also, fat cells store toxins, which can damage the brain even more,' Amen said.
Although this is one of the larger studies linking obesity with brain dysfunction, it isn’t the first, he added. Previous research using similar methods has found obesity is linked to more limited brain function, particularly in elderly people.
'What makes our study different is the focus on brain blood flow, which can show greater sensitivity and earlier changes related to brain dysfunction,' Amen said.
The good news is that weight loss and subsequent weight maintenance can play a significant role in lowering inflammation, which helps brain health. Brains can be improved with a 'healing environment' that includes habits like exercise and eating nutritious foods, he said.
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