"Our research looked at a large group of people and found obesity, specifically around the middle, may be linked with brain shrinkage".
The new findings, published today (Jan. 9) in the journal Neurology, suggest that the combination of obesity (as measured by body mass index, or BMI) and a high waist-to-hip ratio may be a risk factor for brain shrinkage, the researchers said. They looked at nearly 1,000 people, with an average age of 55, accounting for all kinds of other factors that could potentially sway the results, such as age and how physically active they were.
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.
Mark Hamer of Loughborough University, who led the study, said that previous research on whether extra body fat was detrimental to brain size had been inconclusive. Fat accumulated around the middle, which would be represented by a high waist-to-hip ratio, tends to have more toxic effects as it tends to surround abdominal organs like the liver, stomach and intestines than subcutaneous fat, which forms under the skin, by triggering inflammation that can drive everything from heart disease to conditions like arthritis.
The study found that people with both a high BMI and high waist-to-hip ratio had the lowest brain volumes, compared with people who had just a high BMI (but not a high waist-to-hip ratio) and people of a healthy weight.
The discovery points to a link between excess body fat and impaired mental ability or dementia. People in the middle, with a high BMI but without high waist-to-hip ratio, had an of 793 cubic centimeters.
This compared with a volume of 798 for around 3,000 people of healthy weight. "It would be good to see if experimentally induced weight loss actually impacts on changes to the brain", says Hamer.
Grey matter in the brain consists mostly of nerve cells while "white matter" is made up of connecting nerve fibres.