In Beating the Dementia Monster, we cited research associating obesity in mid-life with the eventual development of Alzheimer's disease. While I was studying this angle, I encountered researchers who believed, at least based on anecdotal evidence, that this was most notable when the obesity was in the form of visceral fat -- a beer belly. So, for some time, doctors and others have noticed that people with a beer belly in their 40s and 50s are more likely to develop Alzheimer's disease. I thought this had been studied, because I saw it discussed seven or eight years ago. But the definitive study has only been done recently, and it hasn't even been published yet.
Research on this topic was presented this week at the Chicago meeting of the Radiological Society of North America (RSNA). The scientist presenting the research results said belly fat significantly increases accumulation of abnormal amyloid peptides and tau protein, which are precursors to Alzheimer’s symptoms. They noted the accumulations could begin 20 years before the development of symptom. The study also highlighted insulin resistance and low HDL ("good cholesterol") as contributing factors. Of course, insulin resistance leads to type 2 diabetes which is strongly associated with the development of the disease. (Or, type 2 diabetes is simply a later stage of insulin resistance.)
Why should belly fat contribute to Alzheimer's disease? One explanation the researchers proposed was that belly fat reduces blood flow to the brain. Apparently this is a more significant effect with belly fat as opposed to other forms of obesity.
The researchers also noted that addressing belly fat in your 40s and 50s is most effective for reducing the risk of developing Alzheimer's disease.
The researchers studied a total of 80 cognitively normal midlife individuals. The average age was 49.4 years, with 62.5% being female. About 57% were obese, with the average body mass index (BMI) of the participants being 32.31. The participants were subjected to brain positron emission tomography (PET) scans, body magnetic resonance imaging (MRI), and metabolic assessment (glucose and insulin measurements), as well as a lipid (cholesterol) panel. (My doctors used both PET and MRI scans to assess my brain.) Researchers also performed MRI scans of the abdomen to measure the volume of the subcutaneous fat (the fat under skin) and visceral fat (deep hidden fat surrounding the organs).
Mahsa Dolatshahi, M.D., M.P.H., a post-doctoral research associate at the Mallinckrodt Institute of Radiology at Washington University School of Medicine and lead author of the study said, “We investigated the association of BMI, visceral fat, subcutaneous fat, liver fat fraction, thigh fat and muscle, as well as insulin resistance and HDL (good cholesterol), with amyloid and tau deposition in Alzheimer’s disease. Our study showed that higher visceral fat was associated with higher PET levels of the two hallmark pathologic proteins of Alzheimer’s disease—amyloid and tau. To our knowledge, our study is the only one to demonstrate these findings at midlife where our participants are decades out from developing the earliest symptoms of the dementia that results from Alzheimer’s disease.”
Some of the same researchers presented their work from another study showing how belly fat reduced blood flow to the brain. They associated this reduced blood flow with the development of Alzheimer's disease. (I'll note, however, that I have not seen any other research associating blood flow variation with increased susceptibility to developing the disease. It makes sense, but I don't think it's been proven.)
If you want to read more on this research, check here.
