Excess fat in the abdomen would be associated with a decrease in the volume of certain brain areas.
Documented and supported by many scientists, the health risks posed by overweight and obesity are now well known to the general public. In addition to cardiovascular complications, people with a body mass index (BMI) greater than 30, and therefore considered obese, are prone to type 2 diabetes, exposed to a higher risk of cancer, mainly colon and breast, and suffer more from osteoarthritis.
What we did not know until a few years ago was that obesity can also have consequences for brain development. “Existing research has linked brain shrinkage to memory decline and an increased risk of dementia, but research investigating whether excess body fat protects or harms brain size has been inconclusive” , explains Professor Mark Hamer, of the University of Loughborough, England. “Our research looked at a large group of people and showed that obesity, particularly in the stomach area, may be linked to brain shrinkage.”
The determining measure of the waist-to-hip ratio
His study, published in Neurology, the medical journal of the American Academy of Neurology, sheds light on the impact abdominal body fat has on brain size. To study it, the team based itself on the study of 9,652 people aged 55 on average. 19% of them were obese. Each participant’s BMI, waist-to-hip ratio and overall body fat were measured.
The waist-to-hip ratio is calculated by dividing the waist circumference by the hip circumference. The higher the ratio, the larger the person’s belly compared to their hips. For example, a man with a waist-to-hip ratio greater than 0.90 and a woman with a ratio greater than 0.85 are considered centrally obese.
The team of researchers finally calculated the size of the brain using an MRI and examined the volumes of brain white and gray matter. Gray matter comprises the majority of the brain’s 100 billion nerve cells, as well as brain regions involved in self-regulation, muscle control and sensory perception. The white matter of the brain contains bundles of nerve fibers connecting the various regions of the brain.
A decrease in the volume of gray matter
Before drawing any conclusions, the scientists took into account a number of factors that affect brain volume including age, high blood pressure, level of physical activity and smoking. They were then able to see that although a high BMI alone was linked to a slightly lower brain volume, those who had a high BMI and a waist-to-hip ratio had a lower gray matter brain volume than participants who did not have not a high waist to hip ratio.
Specifically, the researchers found that 1,291 people with a high BMI and a high waist-to-hip ratio had the lowest average gray matter volume of 786 cubic centimeters, compared to 3,025 people with a “normal” weight and volume. average gray matter of 798 cubic centimeters. The 514 people with a high BMI but not a high waist-to-hip ratio had an average volume of 793 cubic centimeters. The scientists, on the other hand, found no significant difference in the volume of white matter in the brain.
“Although our study revealed that obesity, especially towards the ventral level, was associated with a decrease in the volume of gray matter in the brain, it is difficult to determine whether abnormalities in brain structure lead to obesity. or whether obesity causes these changes in the brain,” says Hamer. “We also found links between obesity and shrinkage in specific regions of the brain. This will require further research, but it is possible that one day, regular measurement of BMI and waist circumference ratio /hips may help determine brain health.”
If the researchers want to be optimistic, they concede that their work has limits. Among these is the fact that only 5% of people invited to participate in the study actually participated. These volunteers tended to be healthier, so the results may not reflect the population as a whole. Case to follow.
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