Posted on Dec 18, 2019, 3 p.m.
According to recent research from Iowa State University, less muscle and more body fat may affect how flexible thinking is as we become older, and changes in parts of the immune system may be responsible.
Findings published in the journal Brain, Behavior, and Immunity may open new avenues to treatments that help maintain mental flexibility in aging adults with sedentary lifestyles, obesity or muscle loss that naturally occurs with aging.
Data from over 4,000 middle aged to older participants of the UK BioBank was examined for direct measurements of lean muscle mass, abdominal fat, subcutaneous fat, and how they were related to changes in fluid intelligence over a period of 6 years.
Those mostly in their 40s and 50s with higher amounts of fat in their mid section were discovered to have worse fluid intelligence as they grew older; greater muscle mass appeared to be a protective factor, and after taking into account factors such as age, level of education and socioeconomic status these relationships remained the same.
"Chronological age doesn't seem to be a factor in fluid intelligence decreasing over time," said assistant professor Auriel Willette. "It appears to be biological age, which here is the amount of fat and muscle."
People typically begin to gain fat and lose lean muscle once they reach middle age, which is a trend that continues with age making implementing exercise routines to maintain lean muscle becomes more important to overcome this trend. Exercise, especially resistance training is essential for middle aged women who tend to have less muscle mass than men.
Previous studies show that those with higher BMIs tend to have more immune system activity in their blood that activates the immune system in the brain and causes problems with cognition. BMI only takes into account total body mass making it unclear whether fat, muscle, or a combination of both jump start the immune system; this study investigated whether or not changes in immune system activity may explain links between fat or muscle and fluid intelligence.
Findings showed in women the link between more abdominal fat and worse fluid intelligence was explained entirely by changes lymphocyte and eosinophils white blood cells; while in men changes in basophils white blood cells explained roughly half of the fat and fluid intelligence link. Muscle mass was protective, but the immune system did not appear to play a role. Correlations were also found between body fat and decreased fluid intelligence, but it is unknown if it could increase the risk of Alzheimer’s disease.
"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," said Dr. Brandon Klinedinst.
"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," Willette adds.
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