09/17/2013 11:12 am ET Updated Nov 17, 2013

Brain and Brawn: The New Use It or Lose It

For some time we have known that exercise is necessary to maintain muscle mass. But recent research suggests that a sedentary lifestyle puts both muscle and mind at risk. It appears as if physical exercise can prevent the loss of brain volume associated with aging in sedentary populations.

The new mantra is: "Use muscle or lose brain."

Using magnetic resonance imaging (MRI), UCLA investigators attempted to determine how lifestyle affects brain structure. They did this by measuring test subjects gray matter.

Their what? Does gray matter?

Hang on for a very brief brain anatomy review.

The brain is made up of gray and white matter. Gray matter occupies 40 percent of the brain and is composed of nerve cell bodies, white matter fills the remaining 60 percent of the brain and consists of nerve fibers. These fibers are insulated with myelin (a white substance) to improve the transmission of nerve signals. Processing occurs in the gray matter while white matter connects gray matter areas in the brain.

So yes, gray matters.

The researchers reviewed MRI scans collected over 20 years from 876 individuals enrolled in the Cardiovascular Health Study. The average age was 78, and 42 percent were men. Most were overweight (average BMI of 27 kg/m2) and 25 percent had been diagnosed with Alzheimer's disease or mild cognitive impairment (MCI). The investigators controlled for head size, age, gender, BMI, diseases affecting brain volume, Alzheimer's disease and MCI.

The Minnesota Leisure Time Physical Activity Questionnaire was used to assess caloric expenditure. The most active group burned an average of 3,434 kcal/week compared with 348 kcal/week in the least active cohort.

In the most active group, the average gray matter volume was 663 mL compared with 628 mL in the least active. That's a big difference. It is also noteworthy that the loss of gray matter occurred in brain areas responsible for memory and learning.

This suggests that a physically active lifestyle helps preserve cognitive function. If you want to keep your marbles and your muscles, you better do more than Sudoku.

Use it or lose it.

For more by Paul Spector, M.D., click here.

For more on personal health, click here.

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