How Obesity affects Brain?

How Obesity affects Brain?

 

In the United States, obesity is a growing public health problem among middle-aged and older adults

Studies suggest that obesity affects the activity and size of brain volume. Many pieces of evidence of negative cognitive and brain health consequences caused by obesity are found. High body fat is linked to the shrinkage of brain volumes.

What causes obesity?

Researchers have discovered several gene mutations that lead to obesity. These genes influence the feeding behavior of an individual.

One of the genetic defects, though rare, is curable with a daily injection of “Leptin”. “leptin” is a recombinant protein.

The link between Belly fats and Lower Brain Volume

A recent study has found a link between belly fats and lower brain volume.

In a study, the researchers analyzed 12,087 people living in the United Kingdom with an average age of 62.

MRI scan of all participants was performed. During his study, brain’s gray- and white-matter were studied. Body fats of all participants were studies using a method known as “Bioelectrical Impedance”. During this procedure, small electric currents are passed through the body to estimate a person’s percentage of body fat.

Studies of the link between Obesity and Brain Shrinkage  

Studies suggest that obesity affects brain size and volume. Many brain scans are performed which shows the following changes in the brain linked to body fats percentage:

  • Changes in Grey Matter

During the analysis of brain scans, it was found that higher levels of body fat caused were linked to the shrinkage of brain volumes certain points. It was found that higher body fats affected the volumes of grey matter.

Grey matter is the part of the nervous system which contains nerve cells and is important for the transmission of messages.

In another study, Brain MRI scans of two participants were analyzed. Both the patients were women aged 65 years. One woman had 13% body fat while the other had 49% body fats. The result of MRIs showed that the women having 49% of body fats had lower gray matter volumes in the central brain areas as compared to the other women.

  • Changes in White Matter

The studies conducted at Leiden University Medical Center in the Netherlands showed that body fats percentage causes changes in the brain’s white matter. White matter is the tissue in the brain made up of nerve fibers. These fibers are covered by myelin and give white color to white matter. These fibers allow the areas of the brain to communicate.

Who is more at Risk?

The studies published in the Journal of Radiology suggested that the link between body fat and brain volume was stronger among men as compared to women, but both get affected in a certain way.

In Men

Studies found that in men high levels of body fat were linked to followings:

  • Lower gray matter volume overall
  • Lower volumes in certain gray matter areas in the center of the brain.
  • Other areas affected are a caudate nucleus, thalamus, hippocampus, globus pallidus, nucleus accumbens, and putamen. These areas of the brain are involved in the brain’s reward circuit. These also help in the regulation of the body’s movements.

In women

Researchers found that high body fat is linked to a reduced volume of globus pallidus.

Studies show that both men and women having high body fat levels showed lower brain volume at certain parts.

How Obesity Lowers Brain Volume?

The answer to the question that how body fat levels are linked to reduced brain volume? Is not clear.

Some studies suggest that the high levels of body fats may cause the inflammation of brain tissue. Researchers said that the smaller brain volumes found indicates the possible loss of neurons in those areas. Obesity lowers brain volume in the following ways:

  • Desensitization of Brain

Studies suggest that Gaining weight may desensitize the brain.

In a study published in the Journal of Neuroscience, the researchers scanned the brain of women as they drank a glass of milkshake.

It was observed that sugary drink activated an area known as “striatum”. After half a year, this experiment was repeated on the same women (some of whom gained weight during this period). The women who gained more weight, their brains responded less to the milkshake in the second experiment.

  • Increase in Impulsiveness

A study presented in 2019, at the American Academy of Child and Adolescent Psychiatry meeting in New York showed that in obese children, “orbitofrontal cortex” appeared shrunken compared to lean children.  This is the region of the brain, which controls impulsive. This study hasn’t confirmed a cause-effect link.

It is assumed that the children’s obesity reduced the size of their “orbitofrontal cortex”.  It has possibly caused changes in the immune system, boosting inflammation in the body. The increased inflammation may have an impact on the brain.

The researcher Dr. Antonio Convit, of the New York University School of Medicine said that this has possibly also lead to a “vicious cycle”, in which obesity leads to inflammation. This inflammation damages certain parts of the brain. Then, the damage of brain cells leads to more disinhibited eating and causes more obesity.

  • Stress and Inflammation

A study published in the journal Annals of Neurology described that having higher belly fats are associated with a decrease in brain volume.

Extra fats induce inflammation of body cells, which increases stress on the body. In this way, inflammation and stress impact the brain.

Studies also suggest that the visceral fats (fats between the organs in the abdominal cavity) induce a reduction in brain size and volume.

Visceral fats release unique hormones, which may impact the body in a different manner and affects the body.

  • Risk of Dementia

Studies have also suggested that obesity reduces the brain volumes of people because excessive fats release unique hormones.  The smaller brain volumes caused by obesity increases the risk of dementia. These people also show poorer results on cognitive tests.

  • Lower Memory

Obesity can cause impairment of memory. It can affect women more after menopause. A study published in the Journal of the American Geriatric Society performed the memory tests for 8,745 women aging 65 to 79. The studies found that a one percent increase in the woman’s body mass index (BMI) was linked to the one percent decrease on a 100 point memory test.

The researchers said that the hormones are released by the excessive fats of the body which causes inflammation and affects cognition. In this way, it causes the impairment of memory.

Current study  

Present studies have only found an association between body fat and the lower brain volume. More studies are required to confirm the link between body fats weight and brain volume.

Sources

https://newsroom.clevelandclinic.org/2019/03/12/can-obesity-impact-the-size-of-your-brain/

https://www.neuroscience.cam.ac.uk/research/cameos/ObeseBrain.php

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5410624/

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