People with high levels of body fat stored in their belly or arms may be more likely to develop diseases like Alzheimer’s and Parkinson’s than people with low levels of fat in these areas, according to a study published in the July 24, 2024, online issue of Neurology^®, the medical journal of the American Academy of Neurology. The study also found that people with a high level of muscle strength were less likely to develop these diseases than people with low muscle strength

Researchers have discovered that those who carry weight in these areas – often dubbed ‘beer bellies’ and ‘bingo wings’ — appear to have a higher risk of the diseases, while people with more muscle are at a lower risk

The new study suggests that the impact of obesity is nuanced and related more to specific body composition rather than weight alone

“We consistently observed an increased risk with ‘central obesity’ [characterised by fat mass mainly in the torso] and ‘arm-dominant fat distribution’ patterns, and a reduced risk with the ‘muscle strength’ pattern, in both clinical neurodegenerative disease onset and brain ageing markers,” says lead study author Shishi Xu, MD, a researcher with the department of endocrinology and metabolism at Sichuan University’s West China Biomedical Big Data Center in Chengdu.

“This confirmed our hypothesis that it is not the absolute weight of fat and muscle, but their distribution and quality that significantly impact the development of neurodegenerative diseases”

Body Composition Makes a Difference

For the analysis, Dr. Xu and her colleagues examined health data from more than 400,000 people, the average age being 56. At the outset, the study’s participants were free of neurodegenerative diseases and measured for specific body composition elements, such as waist and hip size, grip strength, bone density, and fat and lean mass

During an average of nine years of follow-up, about 8,200 subjects (about 2 per cent) developed neurodegenerative diseases – mainly Alzheimer’s disease, other dementia-causing diseases, and Parkinson’s disease

After adjusting for other factors that could influence the rate of these disorders (such as high blood pressure, smoking and drinking status and diabetes), the investigative team calculated that adults with high levels of belly fat were 13 per cent more likely to develop these diseases compared with adults with low levels of belly fat

But it’s not just the belly that matters to memory loss, according to the study. Arm fat appeared to be slightly more predictive of dementia development. Those with high levels of arm fat had an 18% greater risk of being diagnosed with Parkinson’s, Alzheimer’s or another form of dementia

The findings aren’t all bad news, though. People with “high muscle strength” faced a 26% lower risk of these neurodegenerative diseases

Male participants with high levels of body fat in their bellies developed neurodegenerative diseases at a rate of 3.38 per 1,000 person-years, compared to 1.82 cases per 1,000 person-years for those with low levels of body fat in their bellies. For female participants, the rates were 2.55 for high levels and 1.39 for low levels. Person-years represent both the number of people in the study and the amount of time each person spends in the study

What does body fat have to do with brain health?

“In simple terms, fat accumulation in the abdomen and arms appears to have a ‘poisonous’ and ‘inflammatory’ effect on other organs, including the cardiovascular system and neurological health, leading to a higher risk of degenerative diseases,” says study author Huan Song, a professor of epidemiology at Sichuan University in China.

Scientists, including Song, believe that high levels of fat, especially around someone’s middle, influence dementia risks indirectly. “Central obesity, characterised by excessive abdominal fat, is associated with metabolic syndrome, inflammation and insulin resistance, all of which contribute to the risk of cardiovascular diseases and, consequently, neurodegenerative diseases,” according to Dr. Thomas Holland of the RUSH Institute for Healthy Aging

It’s not yet entirely clear exactly how heart disease and conditions like Alzheimer’s are related. It may be that the same risk factors — including obesity, lack of exercise, high cholesterol and smoking — raise risks for both or that one can lead to the other. But, according to a review published in the Journal of the American Heart Association, the prevailing theory is that the link has something to do with high blood pressure and the hardening of the arteries, which trigger cell-damaging inflammation and a reduced supply of oxygen to the body and brain. In turn, these problems are thought to contribute to the development of issues such as plaques in the brain while simultaneously limiting our biological ability to clear out these toxic deposits

And while any form of obesity puts a person at greater risk for cardiovascular disease, belly fat is more predictive of more profound, systemic inflammation. “The location of fat, particularly around the abdomen, indicates a higher likelihood of … metabolic complications” that damage the cardiovascular system and, consequently, the brain, Holland says. Arm fat’s link to heart and brain diseases is less established, but Song and her team suspect it, coupled with low levels of strength, may be a predictor of dementia risks, too

How to reduce fat and build strength to combat dementia and Parkinson’s

The study’s findings suggest that simple modifications to reduce belly and arm fat while improving strength can go a long way toward reducing your risks of both dementia and Parkinson’s. “To reduce the risk of neurodegenerative diseases, it is crucial to focus on a balanced diet,” says Holland. “Limiting the intake of foods high in trans and saturated fats — such as dark red meat, baked goods, fried foods, fast food, butter and high-fat dairy products — can significantly improve your health,” including by helping to reduce the amount of fat that accumulates around your belly

But it’s not just about eliminating highly processed and fatty foods from your diet, Holland adds. It’s equally important to work on adding heart- and brain-healthy ingredients to your meals. These include nuts, extra virgin olive oil, and fish such as salmon, all of which are rich in omega-3 and omega-6 fatty acids that help maintain brain health. Antioxidant-rich leafy greens and berries also support overall cognitive and cardiovascular health

Incorporating regular exercise into your routine can help improve strength and burn fat, helping to lower dementia risks. Holland recommends getting 150 minutes of moderate to vigorous physical activity a week, which you can get by doing a 30-minute session of exercise for five days. “This routine should include weight training exercises two to three times a week to build muscle strength, along with stretching and balance exercises to enhance flexibility and stability,” Holland says. “These activities contribute to better cardiovascular health and a lower risk of developing neurodegenerative diseases”

Several limitations existed. The team mainly noted that participants were largely white people from the UK and Northern Ireland, leading to a less diverse sample size

‘Further research involving diverse ethnic cohorts is essential to confirm our findings,’ the researchers concluded