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Why fat-locked muscles are hard to heal and stay strong

We praise Wagyu for its rich marbled flavor in the steak, but the same fat embedded in our own muscles may quietly destroy our strength.

A new study from the University of Florida shows that intramuscular fat not only coexists with weak muscles, but also actively recovers and recovers. The study was published on July 15 Cell Reportsindicating that fat cells infiltrate injured muscles create a physical barrier that prevents new muscle fibers from forming and maturing, resulting in smaller, weaker muscles that fail to produce normal forces.

Fatty is an obstacle, not a bystander

The focus of the study is a disease called intramuscular adipose tissue (IMAT), which is common in obesity, type 2 diabetes, neuromuscular diseases, and aging. So far, it is not clear whether this fat is only present with muscle decline, or whether it plays a more active role in solving the problem. Daniel Kopinke, senior writer and associate professor at UF Medical School, wants to find out.

“Now, we have functional evidence that this is a positive driver of muscle decline,” Kobbink said in the university edition.

Using a mouse model called genetic engineering mfatblockthe group is able to prevent fat from forming in injured muscles. This allows researchers to compare the healing of fat-free muscles with the healing of fat-infiltrated muscles.

Major findings from the study

  • Adipocytes physically prevent new muscle fibers from forming after injury.
  • IMAT limits the fat of muscles to absorb 12% of the amount, limiting the space for recovery.
  • Without fat, muscles regenerate at higher fiber density and produce more force.
  • The effect is caused by physical disorders rather than inflammation or hormone signals.

Kopinke explained: Think of it as a forest fire: if the boulder is on the road, you will not be able to regenerate trees. Similarly, if the fat cells have absorbed the space, the muscles cannot regenerate fibers.

Not just muscle weakness

This has an effect beyond sports injury. IMAT accumulation is a hallmark of chronic diseases such as Duchenne muscle dystrophy and ALS. Sometimes, clinicians can even track the progression of the disease by observing the fat in the muscles in the MRI scan.

“This translates directly into losing power,” Cobbink said. The fat-infiltrated muscles in the study were unable to produce the same force as those without fat. Even if regeneration occurs, the new fiber is smaller and has less function.

Can we shrink fat?

Yes, it’s the hopeful part of the story. The team noted that like fat elsewhere in the body, Imat responds to energy balance. Diet and exercise produce calorie deficiencies may reduce intramuscular fat over time.

“You can shrink fat cells,” Cobbink said. “If the area occupied by adipocytes in the muscle is smaller, the muscle fibers will have more room to grow.”

Rethinking muscle loss

So far, most treatments for muscle damage or disease have focused on encouraging new muscle growth. But this study shows that eliminating barriers like IMAT may be just as important. This shift in perspective could affect how doctors approach everything from exercise recovery to age-related muscle loss.

As Kopinke puts it, “By cleaning up the path to the right healing muscles, we may be able to restore function and increase the strength of millions of people affected by these debilitating conditions.”

Journal Information

Magazine: Cell Reports
doi: 10.1016/j.celrep.2025.116021
Article title: Intramuscular adipose tissue limits functional muscle recovery
Publication date: July 15, 2025

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