The Intersection of Muscle, Fat, and Cognitive Decline: What You Need to Know

When we think about muscles, we often picture them on a sliding scale of size—are you strong with big, bulging muscles, frail with little muscle tone, or somewhere in between? But beyond muscle size and how visible they are due to body fat, there’s another key factor: muscle quality. As we age, preserving not just muscle mass, but also muscle quality, becomes increasingly important. Preventive Neurologist, Dr. Kellyann Niotis, and movement specialist, Beth Lewis, explain the benefits of high quality muscle, not only for maintaining physical strength, but also for supporting brain health.

What Happens to Muscle as We Age?

One of the many changes associated with the aging process is the increased accumulation of intramuscular fat. This fat behaves much like visceral fat, the fat deep within the abdominal cavity surrounding organs, but instead is stored between muscle fibers, altering muscle structure and function. It impacts how muscles contract, and this fat buildup diminishes the muscle’s ability to generate strength. This decline in muscle quality is a major reason people lose strength with age, even if they continue to work out and build lean mass.

The challenge is that even though you may be building muscle, the quality of that muscle doesn’t always improve. Without the ability to properly contract, the brain loses many of the neurotrophic benefits—proteins that support neuron growth and brain function—that come from strong, functioning muscles.

The Vicious Cycle of Insulin Resistance and Muscle Quality

Another factor that contributes to poor muscle quality is insulin resistance. It’s a tricky issue because insulin resistance can create a feedback loop with muscle quality. Dr. Kellyann Niotis explains:

“So we understand that the higher muscle mass that you have, the better your muscles are in terms of taking up glucose from the periphery to lower your blood or fasting glucose levels. Well, over time, what high blood glucose levels and insulin resistance does, is it causes this accumulation of fat inside the muscles, which makes it a little bit harder for you to actually get the benefits of all of that strength training. You have to really work hard to overcome that insulin resistance to try to get your muscles really optimized and working the way that they should be working because the glucose itself can be so toxic.”

Strength Training, HIIT, and Nutrition: The Essential Trio

When it comes to improving muscle quality, strength training alone isn’t enough. High-intensity interval training (HIIT) is another essential piece of the puzzle. While cardio is helpful for fat loss, HIIT is particularly effective because it combines fat-burning with hypertrophy (muscle growth) and power development. This is especially important for aging populations or those with neurodegenerative conditions, as power output is key to maintaining mobility and function.

But there’s more to it than just exercise. Without the right nutrition, you won’t see significant improvements in muscle quality or fat loss. A well-rounded approach combining strength training, HIIT, and proper nutrition is the most effective way to improve muscle quality, reduce fat deposition, and promote brain health. Fitness expert, Beth Lewis, emphasizes that, “you need all three. You can't just do one. You can't just do two. You have to do all three to make changes.”

HIIT not only improves physical fitness but also has direct benefits for the brain. Research shows that HIIT can enhance cognitive function in the short term, improving concentration, processing speed, memory, and attention. It also boosts blood flow to the brain and stimulates the production of neurotrophic factors like Brain-Derived Neurotrophic Factor (BDNF), which supports neuroplasticity and the generation of new neurons. This can help maintain brain health and potentially delay cognitive decline as we age.

Having excess visceral fat—and likely intramuscular fat as well—can lead to chronic inflammation, which is linked to lower brain volumes. Studies have found that people with higher levels of visceral fat tend to have reduced gray matter and white matter volume in critical regions of the brain, such as the temporal lobe, which is involved in memory and is particularly affected in Alzheimer’s disease.

The Bottom Line: Prioritize Muscle Quality for Long-Term Health

Muscle quality is often overlooked in favor of focusing on muscle mass, but as we age, it becomes clear that the quality of our muscles has a profound effect on both physical strength and brain health. By incorporating strength training, HIIT, and a solid nutrition plan into your routine, you can improve not only your muscle quality but also protect your brain from the negative effects of aging and inflammation.

To learn more about the connection between muscle, fat, and cognitive decline, watch our discussion with Dr. Kellyann Niotis and Beth Lewis in the video above.

By Alicia J. Barber, PhD