Obesity Can Shrink Your Brain 1

Does being overweight harm the brain?

LOUGHBOROUGH. Obese people can have their brains shrunk in certain areas. This is reported by British researchers (Neurology 2019; online January 9).

In their study, they found that the effect is particularly evident in people with trunk-dominated obesity.

However, it is so far unclear whether being overweight triggers the changes in the brain - or whether a changed brain promotes the development of obesity. The scientists also did not investigate the question of what consequences the identified brain changes have.

It is not yet clear whether being overweight poses a risk to the brain - and if so, to what extent. Researchers had found evidence of this in several studies in the past.

In 2017, for example, a study by the Max Planck Institute for Cognitive and Neurosciences in Leipzig showed that obesity can impair important brain networks and increase the risk of Alzheimer's disease (Hum Brain Mapp 2017; 38: 3502-3515).

A US study had already shown in 2010 that obesity accelerates the biological aging of the brain (Hum Brain Mapp 2010; 31: 353-64).

Data from almost 10,000 people evaluated

The British researchers led by sports medicine specialist Professor Mark Hamer from Loughborough University investigated how obesity specifically affects the gray matter in the brain.

"Research has linked a shrinkage of the brain with a deterioration of the memory and an increased risk of dementia," said Hamer in a communication on the study. "So far, however, it has not been clear whether additional body fat protects or damages the size of the brain."

For the study, the researchers evaluated data from 9652 people with an average age of 55 years. Almost 19 percent of the participants were considered obese - they had a BMI of 30 or more.

However, as is well known, the BMI has come under fire in recent years, as even people with a lot of muscle mass or a higher bone density can have a very high BMI simply by focusing on their weight.

The doctors therefore also included the body fat percentage and the waist-hip ratio (THQ) in their analysis. The participants were also asked about their health.

Brain volume determined

The scientists then used MRI to determine the brain volumes for the gray and white matter and also included factors that can influence the brain volume, such as age, physical activity, smoking and high blood pressure.

The key finding: people who had both a high BMI and a high THQ had a lower volume of gray matter than those with a normal THQ. Specifically, the scientists found that the 1291 participants with high BMI and high THQ averaged 786 cm3 had the lowest volume of gray matter.

In comparison, this value was 798 cm in the 3,025 people with a normal weight3. The 514 participants with a high BMI but normal THQ had an average of 793 cm3 Gray matter. In contrast, no differences were found for white matter.

Japanese studied the effects of being slightly overweight

Japanese physicians had already published similar results last year, but their work focused on the effects of being slightly overweight (Obes Sci Pract 2017; online December 6).

Although they found that obesity, especially in the core, is related to a lower volume of gray matter in the brain, it remains unclear whether abnormalities in the brain structure lead to obesity or whether obesity causes these changes in the brain, says Hamer.

Another disadvantage of their study is that only five percent of the people invited had taken part in the study - and they were on average healthier than those who had decided not to participate. (dpa)