For years, Body Mass Index (BMI) has been used to measure obesity. However, research now suggests that regional fat distribution may play a more significant role in brain aging and cognitive health.
Recent studies have shown that obesity is linked to structural and functional changes in the brain, including reduced gray matter and impaired connectivity. But BMI can’t capture the differences in fat depots across the body. Visceral fat around organs, leg fat, and other types of fat may affect metabolic pathways differently, leading to varying risks for disease.
A new study published in Nature Mental Health analyzed data from 23,000 adults with different types of fat measured using dual-energy X-ray absorptiometry. The researchers found that arm, leg, trunk, and visceral fat were each associated with distinct patterns of brain atrophy, altered connectivity, and changes in white matter.
Visceral fat was linked to reduced axon density, tissue disorganization, and poorer performance on cognitive tasks such as reasoning, executive function, and memory. The study suggests that regional adiposity, rather than overall obesity, may provide more precise insights into brain aging and cognitive health.
While the findings are modest, they indicate that considering fat distribution, not just BMI, when addressing risks of cognitive decline is essential. Further research is needed to confirm these results and understand the mechanisms behind regional adiposity’s effects on the brain.
Source: https://medicalxpress.com/news/2025-09-bmi-analysis-links-fat-distinct.html