New research, published in the medical journal Neurology has found a curious link between the breadth of your belly with the size and shape of your brain. According to their findings, people with more excess fat around the middle appear to have a shrunken brain and less gray matter.

Scientists at the University College London and Loughborough University in the UK reached these findings by studying the UK Biobank, a vast stockpile of data on individuals' genetics and health. They looked at almost 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.

The findings showed that people with a high BMI alone had slightly lower brain volumes, but those with high BMI and high waist-to-hip ratios were shown to have even less.

In fact, the difference was substantial: people with high BMI and a high waist-to-hip ratio had an average gray matter brain volume of 786 cubic centimeters, while healthy weight people had an average of 798 cubic centimeters. People in the middle, with a high BMI but without high waist-to-hip ratio, had an of 793 cubic centimeters. The white matter, however, did not appear to be affected by obesity.

The link is clear, what it means, however, is less so.

"While our study found obesity, especially around the middle, was associated with lower gray matter brain volumes, it's unclear if abnormalities in brain structure lead to obesity, or if obesity leads to these changes in the brain," study author Dr Mark Hamer said in a statement.

"We also found links between obesity and shrinkage in specific regions of the brain. 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."

Gray matter is made of nerve cells, among other things, and includes regions of the brain involved in muscle control, sensory perception, memory, emotions, speech, decision making, and self-control. White matter, on the other hand, contains nerve fiber bundles that connect various regions of the brain.

It’s unclear what effect this decreased gray matter linked with excess body fat might have on a person in terms of behavior and wider health problems yet. Strangely enough, previous studies have suggested that obesity might actually help to protect against dementia. However, this study appears to affirm the flipside, which suggests obesity could put you at a higher risk of dementia and other conditions affecting the brain.

"Existing research has linked brain shrinkage to memory decline and a higher risk of dementia, but research on whether extra body fat is protective or detrimental to brain size has been inconclusive," said Hamer. "Our research looked at a large group of people and found obesity, specifically around the middle, may be linked with brain shrinkage."