Higher Body Fat Could Make Brain Age Faster While Muscle Protects Against It, Study Suggests

Body fat appears to make our brains get older faster, while muscle mass seems to protect against ageing, according to a study.

Researchers at Iowa State University believe this could be down to how fat cells affect blood cells involved in the immune system.

Previous studies have uncovered links between obesity in middle-aged people and those in early late-life, and worse thinking skills, the team wrote in the Journal of Brain, Behavior, and Immunity. For their research, the scientists wanted to find out more about how different types of body fat affect what is known as fluid intelligence, or the ability to problem solve in new situations.

The study involved 4,431 men and women from the U.K. with an average age of 64. Every two years over a six year period, researchers noted information on the participants including their blood cell counts, and their levels of fluid intelligence.

They found women with more lean muscle mass were more likely to have better fluid intelligence scores over time. But, higher body fat levels were associated with a decline in fluid intelligence in both women and men. In men and women, the declines were linked with lower counts of white blood cells which are part of the immune system.

Existing studies indicate that having a higher body mass index could trigger changes in the immune system that affect the brain, and in turn cause problems with thinking.

Co-author Auriel Willette, assistant professor of food science and human nutrition at Iowa State University, said in a statement: "Chronological age doesn't seem to be a factor in fluid intelligence decreasing over time. It appears to be biological age, which here is the amount of fat and muscle."

Brandon Klinedinst, a PhD student in neuroscience at the institution, explained in a statement that exercising is important for middle-aged women, who on average have less muscle mass than men. Resistance training may be particularly helpful, he said.

Willette said: "If you eat alright and do at least brisk walking some of the time, it might help you with mentally staying quick on your feet."

Klinedinst said it was unclear whether these findings relate to a person's risk of developing the neurocognitive condition Alzheimer's disease, which an esimated 5.8 million Americans are living with.

"Further studies would be needed to see if people with less muscle mass and more fat mass are more likely to develop Alzheimer's disease, and what the role of the immune system is," he said.

Willette told Newsweek: "The most important takeaway is that just because we get older does not mean we get 'less sharp.' The same goes for having less muscle and more fat. It may largely depend on if we take modest steps to maintain our health, regardless of what our body is like, in line with what policy officials recommend."

She added: "Our research will lend more insight into how different parts of the immune system may be having a common effect on the brain impacting how well parts of our brain process information that gives rise to fluid intelligence.

"It also gives us a better understanding of to what degree abdominal fat, fat under the skin (subcutaneous fat), and muscle mass might impact our brain and our ability to 'think on our feet'."

Earlier this year, a separate team of scientists at Yale found eating a diet high in carbohydrates and fat appeared to change the part of the brain that controls the metabolism in a study on mice.

This article has been updated with comment from Auriel Willette.

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A stock image shows a woman thinking. Researchers have looked at the link between body fat and certain thinking skills. Getty