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Hidden belly fat linked to brain inflammation and dementia, study finds
Inflammation from belly fat may be linked to the early stages of
Alzheimer’s disease decades before symptoms begin, new research has found.
“We’ve
known for a while that as the belly size gets larger, the memory centers in the
brain get smaller,” said Alzheimer’s disease researcher Dr. Richard Isaacson, a
preventive neurologist at the Institute for Neurodegenerative Diseases
of Florida.
“This study
shows a brain imaging marker of neuroinflammation which I had not seen
before,” said Isaacson, who was not involved in the new study. “The brain
imaging links the belly fat, or visceral fat, to the brain dysfunction
through an inflammatory cascade.”
The study
found individuals in their
40s and 50s with a greater amount of hidden belly fat “had a higher amount of an abnormal protein called
amyloid in a part of the brain that we know is one of the earliest places where
Alzheimer’s occurs,” said senior author Dr. Cyrus Raji, associate
professor of radiology at Washington University School of Medicine in St.
Louis.
Beta
amyloid plaques in the brain are one of the hallmark signals of
Alzheimer’s, along with tangles of a protein called tau. Amyloid
plaques typically appear first, with tau tangles arriving later as the disease
progresses.
“There’s a
sex difference, as well, where the men had a higher relationship between their
belly fat and amyloid than women,” Raji said. “The reason that’s important is
because men have more visceral fat than women.”
The study
also found a relationship between deep belly fat and brain atrophy, or a
wasting away of gray matter, in a part of the brain’s memory center called the hippocampus.
“That’s
important because brain atrophy is another biomarker of Alzheimer’s disease,”
Raji said.
The brain’s
gray matter contains the majority of brain cells that tell the body what to do.
White matter is made up of fibers, typically distributed into bundles called
tracts, which form connections between brain cells and the rest of the nervous
system.
“We also
found that the individuals with higher amounts of visceral fat tend to have
more inflammation in widespread white matter tracks in the brain,” said lead
author Dr. Mahsa Dolatshahi, a postdoctoral research fellow at Washington
University School of Medicine.
Without a
functional white matter highway, the brain cannot adequately communicate with
different parts of the brain and the body.
‘Pushing the envelope’
Published as a pilot study in the journal of Aging and Disease in
August, Raji and his team originally imaged the brains and bellies of 32 adults
ages 40 to 60. The team kept adding
participants and are now presenting information on an additional 20 people — 52
total — at the Radiology Society of North America’s 2023 conference on Monday.
As more
people were added to the study, details of how inflammation from belly fat on
the parts of the brain where Alzheimer’s originates came into focus. The brain
changes they found were modest, but significant, Raji said.
“The
reason we’ve shown very subtle effects is because we’re looking at midlife —
people in their 40s and 50s — while earlier studies looked at people in their
60s and 70s,” he said. “These are people who, if they do develop Alzheimer’s
disease, it won’t happen for another 20 or 25 more years.
“So, we’re
really pushing the envelope of how early we can detect some of the kind of
subtlest manifestations of abnormalities that can be related to
Alzheimer’s pathology,” Raji added. “By identifying this pathological
link to visceral fat, there are ways we can potentially intervene in this
population.”
Visceral fat and inflammation
When we think of fat, most of us think of subcutaneous fat, the
type you can pinch under your skin or along your waistline. Subcutaneous fat
typically makes up 90% of the body, according to the Cleveland Clinic.
Visceral
fat can’t be poked, prodded or pinched. Visceral fat hides behind the
abdominal muscles, deep in the belly, wrapping itself around vital organs. Both
types secrete hormones and other molecules, but experts say visceral fat is
more metabolically active, sending signals that can trigger insulin
resistance and other health issues.
“Subcutaneous fat is typically not associated with insulin resistance,”
Isaacson said. “The higher the visceral fat level, however, the more a person
has insulin resistance that causes inflammation in the body and the brain.”
Insulin
resistance occurs when cells in the body don’t respond well to insulin, a
hormone essential for regulating blood sugar levels. The condition often leads
to diabetes and a host of other chronic diseases.
“We’ve
hypothesized inflammation in the fat cells leads to insulin resistance, and
that’s fast-forwarded by visceral fat,” Isaacson said. “Insulin resistance then causes inflammation
that fast-forwards amyloid deposition, one of the key markers of Alzheimer’s
disease. That’s why people with diabetes have twice the risk of Alzheimer’s
disease.”
Expensive
full-body MRIs and body scans are the most precise way to measure visceral fat,
but many use estimates based on waist circumference or waist size in proportion
to height. To measure your waist, the Cleveland Clinic recommends wrapping a
flexible tape measure around the waist just above the hips.
“For women,
35 inches (89 centimeters) or more means you’re at risk for health problems
stemming from visceral fat. For men, the number is 40 inches (102 centimeters)
or more,” the clinic states on its website.
“Regardless
of weight, people should find out if they have hidden visceral fat,” Raji said.
“It can be totally missed by using body mass index (BMI) or weight on the
scale.”
That’s
because even thin people can have excess visceral fat. Called “skinny fat” or
“TOFI” (thin outside, fat inside), it can happen when a person exercises but
has a poor diet, and to certain ethnic groups. Asians, for example, have more
visceral fat than Black, White or Hispanic people.
Visceral fat ‘easier to lose’
There’s
good news: Visceral fat responds well to diet and exercise, Raji said. “It is
easier to lose visceral fat from diet and exercise than it is to lose
subcutaneous fat because visceral fat is more easily metabolized and burned.”
There are
multiple things that can target body fat, both from an exercise and nutrition
perspective, Isaacson said.
“Eat a
healthy diet and exercise on a regular basis, which should include muscle
strength training a few times a week, along with fat-burning, less intense cardiofor 45 to 60 minutes, several times a week,” he said.
More tips:
Eliminate or reduce ultraprocessed foods, cut portion sizes, replace
sugary drinks with water, limit processed meats, and reduce meat and high-fat
dairy products, such as cheese and butter, which are packed with saturated
fats, other experts suggest.
Watch
alcohol intake too: It’s not just beer that leads to a “beer belly,” according
to the Mayo Clinic. Drinking alcohol of any kind will expand the waistline.
Watch your
sleep as well. Millions of Americans are sleep-deprived on a daily basis, yet
studies have found people who sleep less than six hours a day have greater
levels of amyloid in their brains.
注释：
Neurodegenerative: adj
表示" 神经变性的"，如：Alzheimer's and Parkinson's are neurodegenerative diseases in which
cell damage and degeneration is seen in certain specific areas of the brain. 早老性痴呆症及帕金森氏症神经退化疾病，是脑的一些特殊部位的细胞出现损坏及退化现象。
neuroinflammation:
n
表示"神经炎症"，如：Our
findings show that this may cause neuroinflammation in the dorsal root ganglion
and neuropathic pain. 我们的研究显示这可能导致背角神经节的神经炎症和神经病理性痛。
visceral:
adj
表示"发自肺腑的；内脏的"，如：So, we really should try to get rid of the excess visceral fat
cells.因此，我们确实应该清除过剩的内脏脂肪细胞。
hallmark:
n
表示" 纯度标记；标志；"，means "a mark on an article of trade to indicate its origin and
authenticity"，如：One hallmark of a good politician
is his ability to influence people. 衡量一个优秀政治家的标志之一就是他影响大众的能力。
tangle:
v; n
表示"缠结"，如：Segmentation
of senile plaques and neurofibrillary tangles is crucial to pathological
analysis of Alzheimer's disease.老年斑和神经元缠结的分割提取对于阿尔茨海默症病理研究有重要的意义。
tau:
n
表示" 希腊文的第19个字母"，means "the 19th letter of the Greek alphabet"
atrophy:
v; n
表示" 萎缩；衰退"，means
"any weakening or degeneration (especially through lack of use)"，如：More exercises can avoid atrophy of cartilage. 多加锻炼可以避免软骨萎缩。
hippocampus:
n
表示"海马"，means
"seahorses"，如：The five amnesiacs in the study
all had serious damage to the hippocampus.研究中的五名健忘患者其海马体都有严重的损伤。
manifestation:
n
表示"表现形式"，means
"a manifest indication of the existence or presence or nature of some
person or thing"，如：She noticed this slight hint of
manifestation of the colour bar. 她注意到了这个微小的种族歧视的表现。
pathology:
n
表示" 病理学"，如：Pathology
is the study of disease.病理学是研究疾病的科学。
subcutaneous:
adj
表示" 皮下的"，means
"relating to or located below the epidermis"，如：Women have a layer of subcutaneous fat.女人有一层皮下脂肪。
prod:
v; n
表示"刺；刺激"，means
"to push against gently"，如：The crisis will
prod them to act.那个危机将刺激他们行动。She gave the man a prod
with her umbrella.她用伞捅了那男子一下。
metabolical:
adj
表示" 新陈代谢的"，means
"of or relating to metabolism"，如：Especially
during exercise, drink mineral water significantly improved fatigue, and speed
up the metabolic rate, the rapid restoration of physical strength.特别是运动时，饮用矿物质水能明显改善乏力状态，加快新陈代谢的速度，迅速恢复体力。
cardio:
n
表示"心动加速中枢"，如：cardio-cerebral syndrome 心脑综合征
ultraprocessed:
adj
表示"超加工的"，如：ultraprocessed
food超加工食品
中文简要说明：
中年发福除了影响体型外观，也可能导致罹患阿兹海默症（一种常见的失智症类型）的风险大增。美国近期一项研究指出，腹部脂肪过多的人，脑部愈有可能出现神经发炎现象，造成大脑失衡、退化，再次佐证肥胖可能是导致失智的元凶之一。
美国有线新闻网（CNN）报导，这项研究由美国圣路易华盛顿大学医学院（Washington University School of Medicine）执行，对象是52位年龄介于40至60岁的成年人。研究团队对他们进行身体扫瞄，以观察腹部脂肪囤积与脑部发炎的关联。
结果发现，内脏脂肪较多的中年人，大脑中淀粉样蛋白（amyloid，一种不可溶的纤维性蛋白质）的含量也较高。淀粉样蛋白在大脑中不正常的堆积，是罹患阿兹海默症的主要特征之一。这样的现象在男性身上也较为明显，因为相较于女性，男性更容易累积内脏脂肪。
该研究也发现，内脏脂肪与掌管大脑记忆的海马回有关。内脏脂肪愈多的人，海马回中灰质的萎缩情形愈严重，而灰质负责讯息的处理与传递。此外，类似的情形也发生在负责传递神经讯息的白质上，「内脏脂肪较多的人，大脑的白质轨道出现更多发炎现象，」该研究领衔作者之一、华盛顿大学医学院多拉沙希博士（Mahsa Dolatshahi）表示。
美国知名的克里夫兰医学中心（Cleveland Clinic）指出，女性腰围若超过89公分，男性腰围超过102公分，就要小心内脏脂肪过多的问题。此外，即使是瘦子也可能拥有偏高的内脏脂肪，可利用体脂计进行测量。根据彰滨秀传医院体重控制中心主任林建华医师建议，正常内脏脂肪数值为男性4-6，女性则是2-4之间。
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