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Hidden Fat Linked To Alzheimer’s Disease

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Almost half of American adults would love to have a slimmer waistline or more slender thighs. Losing this visible fat is a commendable health goal. But there’s another type of body fat that may be of even greater importance to lose, yet you don’t even know if you have it. It’s the fat surrounding our abdominal organs.

Even slim people can carry this highly unhealthy body fat that’s linked to heart disease, stroke, diabetes, and some forms of cancer. Now a new study connects it to Alzheimer’s disease.

Understanding Body Fat

Your body contains different types of fat which can be stored in different ways. The main types of body fat are white, brown, and beige fat cells. And each one plays a different role. For example, there’s:

  • White fat: Which is the most discussed type of fat. It’s made up of large cells that are stored under the skin or around your organs. Its job is to store energy for your body to use later. Some white fat is essential to remain healthy but too much can be harmful.
  • Brown fat: This kind is primarily found in babies to keep them warm, but adults do have a small amount, usually around the shoulders and neck. Researchers have been investigating ways to use brown fat to fight weight gain, obesity, and heart disease.
  • Beige fat: This fat, sometimes called brite fat, can help burn fat rather than store it. Researchers are investigating whether regular exercise helps convert white fat to beige fat.
  • Essential fat: This fat is critical for life and is found primarily in your brain, nerves, bone marrow and the tissues surrounding your organs. Its job is to help regulate hormones necessary for vitamin absorption, temperature regulation and other essential functions.

Body fat is also categorized by location and whether it’s healthy or unhealthy for the body.

Healthy Fat vs. Unhealthy Fat

Subcutaneous fat is fat that’s stored underneath your skin. It’s a combination of beige, brown, and white fat and makes up most of the fat in your body. Subcutaneous fat is the fat you can pinch when you “pinch an inch” around your middle, thighs, arms, or buttocks. Subcutaneous fat is healthy in a normal amount, but too much can lead to trouble such as hormone imbalance.

Then there’s visceral fat…

Visceral fat lies buried beneath the abdominal wall, wrapping itself around key organs such as the liver, pancreas, and kidneys. This hidden belly fat may be out of reach, but this form of fat is biologically active in negative ways, producing compounds that promote low level inflammation, increase insulin resistance, and constrict blood vessels. Previous research has already linked hidden belly fat to poorer cognition.

Visceral Fat Ages The Brain

A study containing 2,364 dementia-free seniors found that those with high levels of visceral fat (belly fat) had significantly lower cognitive function when compared to those with low levels.

Another study on this hidden belly fat published in the journal The Lancet in April 2023 included 8,769 participants aged between 30 and 84. The Mallinckrodt Institute of Radiology researchers found that for each 9½ ounces of excess visceral fat, there was a reduction in cognitive performance equivalent to 0.7 years of cognitive aging.

Their findings represent “causal evidence” that excess visceral fat has a specific role in poorer cognitive function. The latest study went a step further.

Hidden Belly Fat Linked to Alzheimer's Disease

The purpose of the study was to see if visceral fat (belly fat) is connected to the earliest evidence of Alzheimer’s disease, years before symptoms first appear. To find out they enrolled 54 cognitively healthy men and women between the ages of 40 and 60 who were either overweight or obese as measured by body mass index (BMI).

Researchers took measurements of glucose, insulin, blood fats, and blood pressure. Abdominal scans measured visceral and subcutaneous fat, and MRI scans measured the thickness of brain regions affected by Alzheimer’s. A subset of 32 participants had PET scans to examine pathological markers of Alzheimer's disease such as amyloid plaques and tau tangles.

The results showed that a higher visceral fat to subcutaneous fat ratio was linked to higher amyloid in the precuneus cortex. This region of the brain is involved in memories of events in our lives, the location of objects, and the ability to navigate our surroundings. It’s one of the first areas affected by amyloid pathology in Alzheimer's disease. The researchers also found more visceral fat and amyloid in the right precuneus cortex were associated with lower cortical thickness, and more visceral fat (belly fat) was linked to increased brain inflammation and brain atrophy.

Brain Changes Occur As Early As Age 50

The research team published their research in the journal Aging and Disease in August. Cyrus Raji, senior author of the study explained, saying, "This study highlights a key mechanism by which hidden fat can increase the risk of Alzheimer's disease. It shows that such brain changes occur as early as age 50, on average—up to 15 years before the earliest memory loss symptoms of Alzheimer's occur."

He believes targeting visceral fat could become an effective treatment to lower the risk of future brain inflammation, brain atrophy and dementia. Fortunately, shedding excess visceral fat is easier than shedding visible fat.

Visceral Fat Level and Memory Loss

Other researchers agree that more visceral fat is dangerous for the brain and have explored why and how it can rob you of your memory. For example, hidden visceral fat can:

  • Cause Chronic Inflammation: Visceral fat is metabolically active and releases inflammatory cytokines, which are signaling proteins that can promote chronic inflammation throughout the body, including the brain. This inflammation is thought to contribute to the development of Alzheimer's disease by damaging neurons and disrupting normal brain function.
  • Increase Insulin Resistance and Impact Glucose Metabolism: Excess visceral fat is linked to insulin resistance, a condition where cells in the body don't respond effectively to insulin. Insulin resistance can lead to impaired glucose metabolism in the brain. Since the brain heavily relies on glucose for energy, any disruption in glucose metabolism can adversely affect brain function and health, potentially contributing to Alzheimer's disease pathology.
  • Promote Oxidative Stress: Hidden visceral fat can increase oxidative stress in the body by producing harmful substances known as reactive oxygen species (ROS). These substances can damage brain cells and DNA, contributing to the development of neurodegenerative diseases like Alzheimer's disease.
  • Trigger Hormonal Imbalances: Visceral fat affects the secretion and regulation of various hormones that are important for brain health. For example, it can influence levels of adiponectin and leptin, hormones that play a role in regulating metabolism, protecting against insulin resistance and inflammation. Imbalances in these hormones due to visceral fat can adversely affect brain health and contribute to Alzheimer's disease.
  • Damage the Blood-Brain Barrier: Chronic inflammation and oxidative stress caused by visceral fat (belly fat) may contribute to the disruption of the blood-brain barrier (BBB). The BBB is crucial in protecting the brain from harmful substances. When it's compromised, potentially neurotoxic substances can enter the brain, contributing to Alzheimer's disease pathology.
  • Harm Brain Structures: Some studies suggest that this deep belly fat might directly affect the brain's structure and function. For example, a high amount of visceral fat has been associated with decreased brain volume and changes-- like brain atrophy-- in brain regions that are crucial for memory and cognitive functions, which are typically affected in Alzheimer's disease.

Exercise is Key to Losing Visceral Fat

Only an expensive and time-consuming abdominal scan can measure visceral fat with any degree of accuracy but, as a rule of thumb, if a woman has a waist circumference above 35 inches and a man above 40 inches, they are likely to also carry excess subcutaneous fat and visceral fat. Another way to track the healthfulness of your body fat is to use the body mass index. The body mass index is a measure of body fat compared to height and weight. There are a number of body mass index calculators online that can give you your body mass index measurement.

People can also have a slim build, no belly fat and little subcutaneous fat yet carry excess internal, visceral fat. A person is more likely to be a TOFI (thin on the outside, fat on the inside) if they do little or no exercise. And this gives us the key to losing visceral fat whatever a person’s size.

For instance, sumo wrestlers eat 5,000 calories a day and can have a BMI of 56 yet have very little internal fat. That’s because they undergo intense physical training each day. So, to lose visceral fat, aerobic exercise and strength training are important to carry out most days of the week. This will also help protect you against insulin resistance.

Fighting Stress Can Help Eliminate Excess Visceral Fat

Stress can also play a role in building both visceral and subcutaneous fat, so find a relaxation technique or activity to counter stress. Finally, avoid ultra-processed foods and eat a diet based on healthy sources of protein, whole grains, legumes, vegetables, fruits, nuts, and seeds.

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