Belly fat has long been thought to be particularly bad for your heart, but now, a new study adds more evidence to the idea that it may also be bad for your brain.

  The study, from the United Kingdom, found that people who were obese and had a high waist-to-hip ratio (a measure of belly fat) had slightly lower brain volumes, on average, compared with people who were a healthy weight. Specifically, belly fat was linked with lower volumes of gray matter, the brain tissue that contains nerve cells.

  “Our research looked at a large group of people and found obesity3, specifically around the middle, may be linked with brain shrinkage,” lead study author Mark Hamer, a professor at Lough borough University’s School of Sport, Exercise and Health Sciences in Leicester shire, England, said in a statement.

  Lower brain volume, or brain shrinkage, has been linked with an increased risk of memory decline and dementia.

  The new findings, published 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.

  However, the study found only an association between belly fat and lower brain volume, and cannot prove that carrying more fat around the waist actually causes brain shrinkage. It could be that people with lower volumes of gray matter in certain brain areas are at a higher risk of obesity. Future studies are needed to tease out the reasons for the link.