"We also found links between obesity and shrinkage in specific regions of the brain".
Body fat is linked to a number of adverse health effects, including increased risk of heart disease, type-2 diabetes and breathing problems. Of that group, 19 per cent were obese, according to their body mass index (BMI), calculated as weight in kilograms divided by height in metres squared.
In the new study, the researchers analyzed information from more than 9,600 people living in the United Kingdom, with an average age of 55.
However, those with both a high BMI and high waist-to-hip ratio had an even lower grey brain matter volume than participants who did not have a high waist-to-hip ratio.
"It's unclear if abnormalities in brain structure lead to obesity or if obesity leads to these changes in the brain", study author Mark Hamer said in a statement.
The study, published in the journal Neurology, found no significant differences in white matter volume. "This will need further research but it may be possible that someday regularly measuring BMI and waist-to-hip ratio may help determine brain health".
About 500 participants with a high BMI but not a high waist-to-hip ratio also had an average amount of grey matter. People with both high BMI measurements and high waist-to-hip ratios, on the other hand, showed the lowest grey matter volumes.
New UK research has found that carrying extra body fat, especially around the waist, may be linked to a smaller brain size, which could indicate a higher risk of dementia.
Though the study didn't look at potential mechanisms linking visceral fat and brain shrinkage, one hypothesis is that this type of fat is thought to produce inflammatory substances that may play a role in brain atrophy, the researchers said.
Grey matter in the brain consists mostly of nerve cells while "white matter" is made up of connecting nerve fibres.
"All this goes to show that good general health is very important for good brain health", Devi told Live Science.
This compared with a volume of 798 for around 3,000 people of healthy weight.