How your body fat could predict your risk of Alzheimer’s 20 years before symptoms
ALZHEIMER’S disease could be detected up to 20 years before symptoms start to show, as scientists say that body fat could predict your risk of the condition.
Researchers have linked a specific type of body fat to abnormal proteins in the brain that are hallmarks of the most common cause of dementia.
Fat that surrounds vital organs in middle age – known as visceral fat – could indicate your likelihood of developing Alzheimer’s up to two decades before the earliest symptoms appear.
But making lifestyle modifications targeted at reducing the fat could influence the development of Alzheimer’s, the American research team noted.
Lead author Dr Mahsa Dolatshahi said: “This crucial result was discovered because we investigated Alzheimer’s disease pathology as early as midlife – in the 40s and 50s – when the disease pathology is at its earliest stages, and potential modifications like weight loss and reducing visceral fat are more effective as a means of preventing or delaying the onset of the disease.”
Up to one million people are believed to be living with dementia in the UK, with numbers forecast to rise.
Alzheimer’s disease is the leading cause of dementia.
For the new study, researchers focused on the link between lifestyle-related factors – such as obesity, body fat distribution and metabolic aspects – and Alzheimer’s disease.
A total of 80 middle aged people with no cognitive issues – whose average age was 49 – were included in the study.
Just over of the participants (57.5 per cent) were obese, and their average body mass index (BMI) was 32.31.
Having a BMI above 30 is considered obese.
All the participants underwent brain positron emission tomography (PET) scans, as well as MRIs, glucose and insulin measurements and a cholesterol test.
MRI scans of the abdomen were performed to measure the volume of the subcutaneous fat – the layer of flab under skin – and visceral fat, the deep, hidden blubber surrounding the organs.
Dr Dolatshahi, of the Mallinckrodt Institute of Radiology (MIR) at Washington University School of Medicine in St. Louis, Missouri, 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.”
She added thigh muscle scans were also used to measure participants’ volume of muscle and fat.
Researchers also looked for signs of Alzheimer’s disease by using PET scans with tracers that bind to amyloid plaques and tau tangles that accumulate in the brains of people with Alzheimer’s disease.
How to lose visceral fat
Where you tend to gain fat depends on your genes, your hormones, your age, as well as whether you’ve gone through the menopause.
But there are several ways you can minimize the accumulation of visceral fat.
Because it’s more readily metabolised into fatty acids, it responds more efficiently to diet and exercise than fat on the hips and thighs.
Here are five ways to shift visceral fat:
- Keep moving – Exercise can help reduce your waist circumference. Even if you don’t lose weight, you lose visceral belly fat and gain muscle mass. Engage in at least 30 minutes of moderate-intensity activity most days, such as brisk walking or bicycling at a casual pace. Also find ways to move more throughout the day, like taking the stairs or standing when you talk on the phone.
- Eat right – eat a balanced diet rich in fruit, veg and protein and low in sugary foods and drinks
- Don’t smoke – The more you smoke, the more likely you are to store fat in your abdomen rather than on your hips and thighs
- Sleep tight – Make sure you’re getting seven to nine hours of snooze a night. Too little and too much can both be detrimental to your middle
- Drink less – Keep alcohol to a minimum to avoid accumulation of visceral fat
Sources: Bupa UK, Harvard Health
The findings, presented at the annual meeting of the Radiological Society of North America (RSNA) in Chicago, revealed that higher levels of visceral fat were related to increased amyloid.
In fact, 77 per cent of the effect of high BMI on amyloid accumulation was pinned to high levels of fat surrounding the organs.
Dr. Dolatshahi said: “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.”
Targeted management of Alzheimer’s risk
The study also showed that higher insulin resistance and lower HDL were associated with high levels of amyloid in the brain.
The effects of visceral fat on accumulation of amyloid were partially reduced in people with higher HDL, according to the findings.
Study senior author Professor Cyrus Raji said: “A key implication of our work is that managing Alzheimer’s risk in obesity will need to involve targeting the related metabolic and lipid issues that often arise with higher body fat.”
Although previous studies have shown the role of high BMI in damaging the cells of the brain, Dr Dolatshahi pointed out that no similar research has investigated the link between visceral and subcutaneous fat and amyloid accumulation as early as midlife.
She added: “This study goes beyond using BMI to characterise body fat more accurately with MRI and, in so doing, reveals key insights about why obesity can increase risk for Alzheimer’s disease.”
The team are also due to present the findings of a study that shows how obesity and visceral fat reduce blood flow in the brain.
In that study, the researchers performed brain and abdominal MRIs on middle-aged men and women with a wide range of BMIs.
They compared blood flow to the whole brain and different regions of the brain in people with high and low levels of visceral and subcutaneous fat.
The high visceral fat group showed lower whole-brain blood flow.
But no significant difference was observed in blood flow in the people with high and low levels of subcutaneous fat.
Prof Raji said: “Knowing that visceral obesity negatively affects the brain opens up the possibility that treatment with lifestyle modifications or appropriate weight-loss drugs could improve cerebral blood flow and potentially lower the burden of and reduce the risk for Alzheimer’s disease.”
Other major Alzheimer's breakthroughs
While experts have warned that dementia diagnoses in England have reached record numbers, there have been a number of recent advances against brain robbing diseases.
From “game-changing” drugs gaining approval to blood tests that can spot the condition years before symptoms, here are other major Alzheimer’s breakthroughs.
- A “game-changing” Alzheimer’s drug called donanemab, that slows mental decline by up to 60 per cent has been approved in the United States. A UK decision on whether the drug will become available to patients in the UK with early symptoms is expected imminently.
- A blood test that detects Alzheimer’s up to 15 years before symptoms emerge is set to be made free on the NHS within a year. The new test is cheaper, easier and at least as accurate as the current diagnosis options and works by measuring levels of a protein in the blood called p-tau217.
- Researchers have developed a first-of-its-kind test that could predict dementia up to nine years before a diagnosis, with 80 per cent accuracy. It involves analysing network of connections in the brain when it’s in “idle mode” to look for very early signs of the condition.
- Scientists have also put AI to the test, developing machine learning models were able to spot early warning signs of the memory-robbing condition up to seven years before Alzheimer’s symptoms appear.
- A woman who has evaded Alzheimer’s disease despite half her relatives getting it could hold the clues to how to prevent it, with scientists pinpointing a particular gene which they think could help prevent Alzheimer’s from progressing.