Obesity is on the rise worldwide. According to the World Health Organization (WHO), nearly 2 billion adults are currently overweight and 650 million of them have obesity.
A study from the University of South Australia found that some types of obesity can lead to a reduction in the brain’s gray matter and investigated its association with risk of dementia and stroke.
In recent decades, obesity rates have increased exponentially all over the world. Some estimates say that 39.8% of adults in the US have obesity, more than 1 in 3. Globally, around 13% of adults have obesity, more than 1 in 10.
The Centers for Disease Control and Prevention (CDC) define obesity as a BMI of 30 or higher and further split obesity into the following classes:
- Class 1: BMI of 30-34.9.
- Class 2: BMI 35-39.9.
- Class 3 BMI 40 or higher (morbid obesity).
The WHO reports that there is an association between overweight or obesity and a range of health problems. These problems include cardiovascular disease, diabetes, musculoskeletal disorders, such as osteoarthritis and even some cancers.
With obesity becoming more and more common, the link between body fat and cognitive health raises an alarm. Researchers report that people with unfavorable or neutral types of obesity are at highest risk of reduction in the brain’s grays matter.
The study published by Anwar Mulugeta, et al. explored the link between body fat and higher risk of dementia or stroke. They found a link between some types of body fat and reduction in gray matter, a part of the brain that contains most of its neurons and is critical to cognitive function.
The lead author said that they found that people with higher levels of obesity, especially those with metabolically unfavorable and neutral adiposity subtypes, had much lower levels of gray matter, indicating that these people may have compromised brain function which needs further investigation.
Gray matter is an essential component of the brain that is rich in neuronal cell bodies, glial cells and capillaries. It is located in different regions of the brain and has multiple roles including learning, memory, cognitive function, attention and muscle control.
Gray matter makes up the outermost layer of the brain. The white matter and grey matter are similar as they are both essential sections of both the brain as well as the spinal cord. The grey matter gets its grey tone from a high concentration of neuronal cell bodies.
Age related cognitive decline and dementia are often associated with reduced gray matter, causing atrophy. Alzheimer’s disease dementia is also associated specifically with hippocampal atrophy, or reduced gray matter in the hippocampus, which extends to other regions as the disease progresses. The quantity of gray matter may signify cognitive health.
The researchers found that individuals with high genetic load for unfavorable adiposity are characterized by fat accumulation around the abdomen and internal organs, high cholesterol and increased risk of type 2 diabetes and coronary heart disease.
Individuals with favorable adiposity have fat accumulation more around the hip and less on the internal organs with lower risk of cardiovascular disease. It is increasingly appreciated that obesity is a complex condition and that excess fat which is located around the internal organs has particularly harmful effects on health.
The study found that for every extra 3 kilograms of body weight in a person of average height, the amount of gray matter decreased by 0.3%.
Mercadante AA, Tadi P. Neuroanatomy, Gray Matter. [Updated 2020 Jul 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK553239/