This study was released today, demonstrating in 6,583 patients that visceral fat mass in the 40s predicts the risk of dementia in old age. Patients in the highest quintile (20% with the most visceral fat mass) had an almost three-fold higher risk of dementia than patients in the lowest quintile. This is a greater effect than you see from "genetics". Overall fat mass was less strongly correlated with dementia. This study is so timely, they must have heard about my blog post.
They used a measure of visceral fat called the "sagittal abdominal diameter", basically the distance from the back to the belly button. In other words, the beer belly.
What we're looking at is another facet of the pervasive "disease of civilization" that rolls into town on the same truck as sugar and white flour. Weston Price described it in 14 different cultures throughout the world in Nutrition and Physical Degeneration. Diabetes, cardiovascular disease, obesity, cancer and dementia all seem to come hand-in-hand. It's hard to say exactly what the root cause is, but the chain of causality seems to pass through visceral fat and insulin signaling in many people.