Do you want to keep your mind sharp as you get older? Build some bulk in your muscles and pay attention to your waist. For the first time, scientists have discovered that having less muscle and more body fat may affect our thinking as we age, and changes in parts of the immune system may be responsible, according to a study by Iowa State researchers.
The study, which was published in Brain, Behavior and Immunity, analyzed six years of data from 4.431 men and women, with a mean age of 64. The researchers examined the participants' changes in the lean mass and body fat abdominal and total, and how those changes in body composition were related to changes in fluid intelligence (or logical problem-solving skills) over the course of the study period.
How much fatter less intelligent?
They found that people in their 40s and 50s who had a greater amount of fat in the midsection, had worse intelligence fluid as they got older. Having more muscle mass, on the other hand, was linked to better fluid intelligence. The body composition-brain power link held regardless of age and education.
«Chronological age does not appear to be a factor in the decline in fluid intelligence over time.said study author Auriel Willette in a press release. «It seems to be the biological age, which here is the amount of fat and muscle«.
This seemingly improbable brain-body composition connection appears to be rooted in how body fat affects the immune system. Previous research has shown that people with a higher body mass index (BMI) have higher levels of immune system activity in their blood, which triggers the immune system in the brain and interferes with cognition.
Skipping those findings, the researchers in this study looked at body fat and muscle separately (since BMI only takes total body mass into account). And they found a clear connection between body fat and increased immune activity. In the women in this study, the entire link between increased abdominal fat and poorer fluid intelligence was explained by changes in two types of white blood cells: lymphocytes and eosinophils. In men, a completely different type of white blood cell, the basophils, explained about half of the intelligence relationship between fat and liquid.
Having more muscle was associated with better fluid intelligence, but there was no strong immune system connection.
«More 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 is the role of the immune system«.
Meanwhile, protecting your mind is just another reason to eat a healthy diet and hit the gym to build muscle.