Excess body fat is well-known to increase the risk of health issues like heart disease and diabetes. Now, however, scientists have found a connection between fat distribution – specifically on the arms and belly – and the risk of developing dementia.
Dementia, a broad term for neurodegenerative diseases including Alzheimer’s, is becoming increasingly prevalent. By 2050, an estimated 139 million people worldwide are expected to suffer from it.
To put that into context, the Alzheimer’s Society reports that one in three people born in the UK today will develop dementia.
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Despite its increasing prevalence, the exact causes of dementia are complex and not fully understood. However, a new study published in Neurology, the medical journal of the American Academy of Neurology, indicates that high levels of body fat in the belly or arms may significantly raise the likelihood of developing this debilitating condition.
“Our significant findings support our hypothesis that it is not merely the absolute weight of fat and muscle, but their distribution and quality, that significantly impacts the risk of developing neurodegenerative diseases,” Dr Shishi Xu, lead author of the study, told BBC Science Focus.
The study involved 412,691 people, 8,224 of which went on to develop neurodegenerative diseases, including dementia and Parkinson’s.
After statistically accounting for other factors that could impact disease rates – namely, high blood pressure, smoking and drinking status and diabetes – the team found that people with high levels of belly fat were 13 per cent more likely to be diagnosed with neurodegenerative diseases.
Meanwhile, people with high levels of arm fat were 18 per cent more likely.
It’s not all doom and gloom, though. The researchers also found that high muscle strength can reduce disease risk by 26 per cent.
“Our study may help build up a more comprehensive causal chain for the relationship between our body and future neurodegenerative risk,” Xu said. “If at the very beginning you can actively modify your body composition, your future risk of neurodegeneration can also be further decreased.”
The team suggests that targeted interventions to decrease belly and arm fat could be more effective for neurodegeneration protection than general weight control.
Xu added, “Modifications like engaging in resistance training, reducing sedentary behaviour and adhering to a balanced diet can effectively reduce abdominal fat as well as enhance muscle strength, which may potentially offer greater neuroprotective benefits than weight-focused anti-obesity medications.”
The findings add to a growing body of evidence that suggests fat is inextricably linked to the risk of developing a neurodegenerative disease.
A study presented at the annual meeting of the Radiological Society of North America in November 2023, for example, tied visceral belly fat in midlife to changes in the brain related to Alzheimer’s.
Further back, in 2018, researchers showed that higher levels of abdominal fat in older adults are associated with cognitive decline.
Still, scientists aren’t sure what the underlying mechanisms behind the relationship are. The dominant hypothesis, Xu explained, “is that fat accumulation in the abdomen and arms appears to have a poisonous and inflammatory effect on other organs, including the cardiovascular system”.
The researchers noted that the link between belly and arm fat and neurodegenerative diseases is partly explained by the occurrence of cardiovascular diseases like heart disease and stroke.
Xu said that the next step for the team is to conduct a series of studies exploring how body composition influences other health outcomes, such as heart failure. Their goal is to build a more complete understanding of fat’s impact on overall health.
About our experts
Shishi Xu is a clinician in the Department of Endocrinology and Metabolism at West China Hospital, Sichuan University in China. Xu completed their PhD at Sichuan University and Oxford University, where she developed a passion for “data”.
Subsequently, Xu became a postdoc at the West China Biomedical Big Data Center at West China Hospital, receiving training in epidemiology and evidence-based research. Xu's research interests include metabolic diseases such as diabetes, obesity and sarcopenia, as well as the construction and analysis of large population cohort data.
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