Excess body weight raises the risk of neurodegenerative diseases, but a study has revealed that it's not just the total weight that always matters, it's the body composition.

Researchers have found that individuals with higher fat accumulation in their belly or arms are at a greater risk of developing Alzheimer's and Parkinson's compared to those with lower fat levels in these areas.

Interestingly, the study published in the journal American Academy of Neurology also highlights that strengthening muscles in these fat hotspots can offer protective effects, suggesting that targeted exercise might be a key strategy in reducing the risk.

"These neurodegenerative diseases like Alzheimer's and Parkinson's affect over 60 million people worldwide, and that number is expected to grow as the population ages, so it's crucial that we identify ways to modify risk factors to develop some preventive tools," Dr. Huan Song, the study author from the Sichuan University in Chengdu, China, said in a news release.

"This study highlights the potential to lessen people's risk of developing these diseases by improving their body composition. Targeted interventions to reduce trunk and arm fat while promoting healthy muscle development may be more effective for protection against these diseases than general weight control," Dr. Song said.

The researchers tracked 412,691 participants, with an average age of 56 for over nine years. At the start, they measured each person's body composition, noting their waist and hip sizes, grip strength, bone density, and fat versus lean mass.

During the study, 8,224 participants developed neurodegenerative diseases, including Alzheimer's, other forms of dementia, and Parkinson's disease. Among men with high levels of belly fat, the incidence rate was 3.38 per 1,000 person-years, compared to 1.82 per 1,000 person-years for those with low levels. For women, the rates were 2.55 for high levels of belly fat and 1.39 for low levels. Person-years help quantify the number of people in the study and the duration of their participation.

After accounting for various factors, the researchers found that individuals with high levels of belly fat were 13% more likely to develop neurodegenerative diseases compared to those with lower levels. Those with high levels of arm fat faced an 18% increased risk. Conversely, individuals with high muscle strength were 26% less likely to develop these diseases compared to those with lower muscle strength.

The researchers attribute the link between body composition and neurodegenerative diseases partly to the onset of cardiovascular conditions like heart disease and stroke during the study.

"This underscores the importance of managing these cardiovascular diseases right away to help prevent or delay the development of Alzheimer's, Parkinson's, or other degenerative diseases," Song said.

However, the study involved predominantly "white people from the United Kingdom of Great Britain and Northern Ireland," limiting the generalizability of the results.

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