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Experts say physical activity is one way to reduce muscle fat. Hugo Abad/Getty Images
  • Researchers say muscle fat in the thighs may indicate a higher risk of cognitive decline in older adults.
  • Experts say fat stored in the body can cause inflammatory conditions that affect the brain.
  • They say these findings highlight the need for older adults to have healthy diets and get daily exercise.

People who store increasing amounts of fat in their muscle tissue over time may be at higher risk of cognitive decline.

That’s according to a new study published in the Journal of the American Geriatrics Society.

Researchers report that increased levels of fat in the thigh muscles over a five-year period was a risk factor for faster and greater cognitive decline in older men and women.

The association between muscle fat — known as muscle adiposity — and loss of cognitive powers was found to be independent of total weight, other fat deposits in the body, muscle strength or mass, and traditional dementia risk factors.

“Our data suggest that muscle adiposity plays a unique role in cognitive decline, distinct from that of other types of fat or other muscle characteristics,” said Dr. Caterina Rosano, PhD, a corresponding study author and a professor of epidemiology at the University of Pittsburgh’s School of Public Health, in a statement.

“If that is the case, then the next step is to understand how muscle fat and the brain ‘talk’ to each other, and whether reducing muscle adiposity can also reduce dementia risk.”

Dr. Rosano and her colleagues used CT scans to measure muscle fat in 1,634 adults ages 69–79 years at year 1 and year 6. Cognitive function was assessed at years 1, 3, 5, 8, and 10.

“It’s well known that, in general, fat is bad for the brain because it releases inflammatory factors into the bloodstream,” Dr. Rosano told Medical News Today.

“We also know that muscle, as an endocrine organ, produces factors that are good for the brain. Physical exercise is good for the brain.”

That knowledge provided the foundation for studying the possible effect of muscle adiposity in the brain, she said.

“Fat is more than meets the eye,” Dr. Rosano said. “It’s something that hides in the body.”

“Intramuscular fat has already been established as a predictor of muscle and mobility function and metabolic health,” said Kelsey Costa, a registered dietitian nutritionist and health research consultant for the group Medical Inspiration Daily for a Stronger Society who was not involved in the study.

“Health issues like diabetes, stroke, and cardiovascular disease are linked to intramuscular fat. These results suggest that intramuscular fat is also an important risk factor for cognitive decline,” she told MNT.

The study findings were similar for Black and white men and women.

Dr. Rosano said that researchers chose to study fat in the thighs because that part of the body contains large muscles where deposits can be easily seen on CT scans.

Ongoing studies are looking at whether fat stored in muscles in other parts of the body also raise cognitive risks.

“We don’t know why it is there, but we can measure it,” Dr. Rosano explained.

“If you have fat in your muscles it means you should be extra careful about other risk factors [for dementia],” she added. These may include:

  • smoking
  • excess weight
  • high blood pressure
  • diabetes

Dieting may not be directly effective in reducing muscle adiposity, but Rosano noted, “Muscle fat is not the only thing that’s bad for your brain.”

“Intramuscular fat accumulation can increase with both age and obesity,” Costa said.

“Therefore, it is essential to maintain a healthy weight and to control excess fat accumulation,” Costa added.

Strategies to maintain intramuscular fat levels within an optimal range may include:

  • dietary changes
  • strength training
  • aerobic exercise
  • improved sleep

University of Pittsburgh researchers are investigating possible pharmacological interventions that might reduce muscle adiposity.

The natural muscle protein myostatin is one possible substance being studied, although Rosano said that treatment “is more likely to be a group of substances, not just one.”

“Interventions aimed at reducing intramuscular fat levels should be actively pursued to determine if this might reduce the risk of cognitive decline in aging populations,” said Costa.

“To prevent or slow cognitive decline, medical professionals should emphasize healthy lifestyle behaviors with a focus on weight management, nutrient-dense eating patterns, and muscle strength/mass maintenance. To maintain muscle health, individuals must consume adequate dietary protein and engage in physical activity, including progressive resistance training.”

– Kelsey Costa, registered dietitian nutritionist