Higher amounts of visceral abdominal fat in midlife are linked to a greater risk of developing Alzheimer’s, according to research just presented at the annual meeting of the Radiological Society of North America (RSNA).
It has been known for some years that obesity is a significant factor in Alzheimer’s disease: this is a finding reported in various studies. Excess weight can cause neuronal changes such as the accumulation of the beta-amyloid protein or the formation of brain damage generally associated with Alzheimer’s disease.
RSNA researchers, however, for the first time have linked a specific type of fat (visceral fat) to the accumulation of the beta-amyloid protein in cognitively normal people. Visceral fat is the fat that surrounds the internal organs located deep (hence called “visceral”) in the belly and not located at a subcutaneous level. According to research, it increases the risk of Alzheimer’s because it is related to changes that occur in the brain up to 15 years before the first symptoms of memory loss of the disease appear.
To demonstrate this, researchers analyzed data from 54 cognitively healthy subjects, aged between 40 and 60, with an average Body Mass Index (BMI) of 32 (which determines first-degree obesity). Participants underwent glucose and insulin measurements, as well as glucose tolerance tests. The volume of subcutaneous fat and visceral fat were measured using abdominal MRI. The brain MRI instead measured the cortical thickness of the brain regions that are usually affected by Alzheimer’s disease. Finally, PET (positron emission tomography) was used to examine the brain for the presence of amyloid plaques and tau tangles, proteins that are believed to interfere with communication between brain cells and are detected in large quantities in the brains of sick people of Alzheimer’s.
The scientists discovered that a higher proportion of visceral fat (compared to subcutaneous fat) was associated, in the subjects examined, with a greater concentration of amyloid (highlighted by PET) in an area of the cerebral cortex known to be the site of amyloid accumulation in Alzheimer’s. This relationship was worse in men than in women, as men physiologically tend to accumulate belly fat, while women do so after menopause. The researchers also found that higher measurements of visceral fat correlated with an increased burden of inflammation in the brain.
“By going beyond body mass index and better characterizing the anatomical distribution of body fat on MRI, we now have a better understanding of why this factor may increase the risk of Alzheimer’s disease,” said the senior author of the study, Dr. Cyrus A. Raji, Associate Professor of Radiology and Neurology and Director of Neuromagnetic Resonance at the Mallinckrodt Institute of Radiology (MIR) at Washington University School of Medicine in St. Louis.
The subcutaneous fat, in fact, which women tend to accumulate on the hips and thighs, has a protective effect against heart attacks and strokes and is anti-inflammatory at a brain level. Visceral fat located on the abdomen is dangerous: it lines the internal organs such as the liver, heart, and blood vessels, can produce pro-inflammatory and pro-tumor substances, and increases the risk of cardiovascular diseases, sexual dysfunction, kidney problems, and some tumors.
For this reason, the advice is to return to your ideal weight as soon as possible if you are overweight, but not only that: a belly is dangerous even in thin people. A previous study published in JAMA found that menopausal women with normal weight but excess abdominal fat had a 31 percent greater risk of all-cause death. The risk was almost the same as in the obese group. This is why it is important to eliminate belly fat for everyone: it is not just a blemish, it is the source of numerous health problems.