Abdominal Fat Linked to Lower Brain Volume in Midlife

New research provides strong evidence of an association between abdominal fat and reduced brain volumes, particularly those involved with cognitive function.

In large study of healthy middle-aged adults, greater visceral and subcutaneous abdominal fat on abdominal MRI predicted brain atrophy on imaging, especially in women.

"The study shows that excess fat is bad for the brain and worse in women, including in Alzheimer's Disease risk regions," lead author Cyrus Raji, MD, PhD, with the Mallinckrodt Institute of Radiology, Washington University, St. Louis, Missouri, told Medscape Medical News.

The study was published online August 28, 2023 in the journal Aging and Disease.

Modifiable Risk Factor

Multiple studies have suggested a connection between body fat accumulation and increased dementia risk. But few have examined the relationship between types of fat (visceral and subcutaneous) and brain volume.

For the new study, 10,000 healthy adults aged 20-80 years (mean age, 52.9 years; 53% men) underwent a short whole-body MRI protocol. Regression analyses of abdominal fat types and normalized brain volumes were evaluated, controlling for age and sex.

The research team found that higher amounts of both visceral and subcutaneous abdominal fat predicted lower total gray and white matter volume, as well as lower volume in the hippocampus, frontal cortex, and temporal, parietal, and occipital lobes.

"The findings are quite dramatic," Raji told Medscape Medical News. "Overall, we found that both subcutaneous and visceral fat has similar levels of negative relationships with brain volumes."

Women had a higher burden of brain atrophy with increased visceral fat than men. However, it's difficult to place the sex differences in context due to the lack of prior work specifically investigating visceral fat, brain volume loss, and sex differences, the researchers caution.

They also note that while statistically significant relationships were observed between visceral fat levels and gray matter volume changes, their effect sizes were generally small. 

"Thus, the statistical significance of this work is influenced by the large sample size and less so by large effect size in any given set of regions," the investigators write.

Other limitations include the cross-sectional nature of the study, which precludes conclusions about causality. The analysis also did not account for other lifestyle factors such as physical activity, diet, and genetic variables.

The researchers call for further investigation "to better elucidate underlying mechanisms and discover possible interventions targeting abdominal fat reduction as a strategy to maintain brain health."