August 7, 2024
People who carry extra fat around their bellies or in their arms may be more likely to develop Alzheimer’s disease than their peers who don’t tend to carry excess fat in these areas, according to a new report. Those with greater muscle strength, on the other hand, may be at lower risk of developing Alzheimer’s disease, the study found. The findings add to growing evidence that body composition may be a factor in determining Alzheimer’s risk.
For the study, researchers looked at 412,691 men and women who were part of the UK Biobank, a long-running study of health among people living in the United Kingdom. Their average age was 56. At the start of the study, researchers gathered information about their body makeups, including waist and hip measurements, grip strength, and the relative amounts of fat and lean body mass.
The researchers monitored them over an average of nine years. During that time, 8,224 had developed a degenerative brain disorder, primarily Alzheimer’s disease and other forms of dementia as well as Parkinson’s disease.
The researchers considered various health and lifestyle factors that could raise the risk of developing Alzheimer’s disease, including high blood pressure, diabetes, smoking or heavy alcohol use. After adjusting for these factors, they calculated that adults with high levels of belly fat at the start of the study were 13 percent more likely to develop Alzheimer’s or other degenerative brain disorders than those with low levels of belly fat. People with high levels of arm fat were 18 percent more likely to develop these diseases than those with low levels of arm fat.
Markers for brain aging were also examined in a subset of participants. People with high levels of abdominal or arm fat also tended to show increased signs of brain aging. People with excess belly or arm fat, for example, had lower volumes of various parts of the brain, including the hippocampus, a region critical for memory formation and one of the brain areas first affected by Alzheimer’s disease. Earlier studies have tied brain shrinkage to a higher risk for Alzheimer’s disease.
The researchers also considered muscle strength, as measured by grip strength. They found that those with higher levels of muscle strength were 26 percent less likely to develop Alzheimer’s disease and other neurodegenerative disorders than those with low levels of strength. The findings were published in Neurology, the medical journal of the American Academy of Neurology.
As with all observational studies, it is possible that belly fat is not a cause of dementia but a sign of an unhealthy lifestyle or some other metabolic illness. But ongoing research continues to suggest that belly fat, and the body changes that go with it, may be bad for the brain over the long term.
Carrying excess weight has been closely linked with diseases that affect the blood vessels, including diabetes, heart disease and high blood pressure. And being apple-shaped, with excess belly fat, as opposed to pear-shaped, with large hips and thighs, has been linked with an increased risk of heart attacks, strokes and diabetes. Such vascular ailments are known to be important risk factors for Alzheimer’s as well.
“This underscores the importance of managing these cardiovascular diseases to help prevent or delay the development of Alzheimer’s, Parkinson’s or other degenerative diseases,” said study author Dr. Huan Song of Sichuan University in China. “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.”
For instance, the authors note, lifestyle modifications, such as regular resistance training and reducing sedentary behavior, can help to reduce central fat and build muscle strength. Eating a heart-healthy diet rich in whole grains, fruits, vegetables and lean meats, and avoiding ultra-processed foods and snacks and sugary drinks, can also help. Alcohol, too, can contribute to “beer belly,” or excess abdominal fat, one more reason to avoid heavy drinking. Such measures, they say, may help to protect the aging brain.
By ALZinfo.org, The Alzheimer’s Information Site. Reviewed by Eric Schmidt, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.
Source: Shishi Xu, MD, PhD; Shu Wen, MD, PhD; Yao Yang, MSc; et al: “Association Between Body Composition Patterns, Cardiovascular Disease, and Risk of Neurodegenerative Disease in the UK Biobank.” Neurology, July 24, 2024.
