The study from the UK found that people with more body fat show differences in brain structure, including lower volume of gray matter, which contains most of the brain’s nerve cells. Past research has linked obesity to a heightened risk of dementia in old age.

Meanwhile, studies have tied gray matter shrinkage to dementia risk as well.

So it is possible the current findings help connect the dots, according to researchers. “Recent studies are showing that being obese has a substantial impact on our hormonal and immune systems, which has been shown to lead to inflammatory reactions that also affect brain tissue,” said lead researcher Dr. Ilona Dekkers, of Leiden University Medical Centre in the Netherlands.

Dr. Harold Bays, a U.S. endocrinologist who was not involved in the study, made similar points that “dysfunctional fat tissue” might directly affect the brain.

People often think of fat as inert tissue that’s simply stored in the body. In reality, he said, fat is “active” tissue.

And when fat cells become excessively large — and accumulate around the heart, intestines, and other organs — they become dysfunctional, churning out hormones and inflammatory substances, a process that contributes to conditions such as diabetes, high blood pressure, and fatty liver disease.