Fat growth around the muscles can be a silent killer

By Dennis Thompson

Health Day reporter

THURSDAY, May 18, 2023 (HealthDay News) — Belly fat is known to be unhealthy when it accumulates around the abdominal organs, but there’s a more insidious form of fat that may be even more dangerous to your health, a new study suggests. .

According to the results published in the journal on May 16, fat infiltrating the muscles dramatically increases the risk of death. Radiology.

Researchers found that fatty muscle — a condition called myosteatosis — was associated with a 15.5% increase in the absolute risk of death in a group of healthy adults.

By comparison, obesity appeared to increase participants’ absolute risk of death by only 7.6%. Fatty liver disease increased the risk by 8.5% and muscle wasting by 9.7%.

“The signal [for muscle fat risk] it was much stronger in this otherwise healthy cohort,” said lead researcher Dr. Perry Pickhardt, chief of the Division of Gastrointestinal Imaging at the University of Wisconsin School of Medicine and Public Health. “It really stood out as a strong biomarker beyond the things that I think we all accept as important measures.

“I think there’s going to be a profiling of patients where if you pair myosteatosis with a very fatty liver or maybe a lot of visceral fat, you can do a lot worse than if you just have one or two of those,” Pickhardt added. .

Muscle fat is of increasing interest in obesity and diabetes, said Dr. Steven Heymsfield, professor of metabolism and body composition at Louisiana State University’s Pennington Biomedical Research Center.

Each muscle cell naturally contains a small and healthy amount of fat that can be used for energy, said Heymsfield, who was not involved in the study.

The real health problem comes from the excess fat that accumulates outside the cells and around the muscle fibers and bundles.

Think of a steak

“If you think about a steak, the marbling of the steak, that’s what we’re dealing with,” Heymsfield said. “Over the last decade or two, it has been shown to be associated with adverse health outcomes, as this study shows.”

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According to Heymsfield, people carry on average a few kilograms of muscle fat in their bodies. It is more likely to accumulate in the legs than in other parts of the body.

Pickhardt and colleagues conducted their study on a group of nearly 9,000 healthy patients who underwent a low-dose CT scan for colon cancer screening between 2004 and 2016, a procedure known as virtual colonoscopy.

The researchers realized that these CT scans could be useful in assessing other potential health problems, given that the scans collect a large amount of data about a person’s body composition.

“If you look at visceral fat and muscle measurements and aortic calcium or liver fat or bone marrow density, all these things add up and you can essentially have this really powerful prognostic virtual physical exam, if you will. to take advantage of that from a CT done for any reason,” Pickhardt said.

“For now, we’re calling it ‘opportunistic filtering’ because we’re taking data that was previously basically ignored or thrown away and using it in new ways,” he added.

Therefore, the research group trained an artificial intelligence tool that can be used to extract body composition measurements from abdominal CT scans, specifically assessing the abdominal fat, muscle fat, liver fat content and muscle atrophy of each person.

Automated software has simplified the process. “It would have taken a lifetime to do this with the older methods,” Heymsfield said.

The researchers then followed the participants for an average of nine years to see if these measures were associated with serious health problems or early death.

Not only was muscle fat associated with the highest risk of death, but this association persisted even after the researchers calculated each person’s BMI (body mass index)—the best available measure of obesity.

Thin people are also at risk

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“BMI was actually a very poor predictor and had a very weak signal,” Pickhardt said. “Clearly, there are patients who were not obese and had this wrong amount of muscle mass. That’s what makes this so important – there are slim people in terms of BMI who actually have a worse profile than you think.”

However, this study cannot establish a clear cause-and-effect relationship between muscle fat and risk of death, noted Dr. Angela Tong, clinical assistant professor of radiology at New York University School of Medicine.

Muscle fat may accumulate due to another health problem that poses the real risk, said Tong, who co-authored the study.

“I think it’s more of a sign that something else is going on, maybe something else in your health that’s not allowing you to be as active,” Tong said. – You should watch it carefully if you have heart problems or diabetes.

Other studies have linked fatty muscles to poor outcomes. For example, a review of evidence published in 2020 Critical Reviews in Oncology/Hematology showed that cancer patients diagnosed with myosteatosis had a 75% higher risk of death than those without fatty muscles.

How does it happen?

It’s not entirely clear why your muscles start to store fat, Heymsfield said.

“There may be some genetics involved and it increases with age despite your best intentions to lift weights or exercise,” Heymsfield said.

Muscle fat also accumulates when your muscles atrophy, Heymsfield said.

“Let’s say you have a cast on your leg and the muscle atrophies, sometimes those muscle cells are replaced by fat cells,” Heymsfield said. “That’s probably the biggest source of what these investigators have found.”

For example, myosteatosis is a hallmark of certain types of muscular dystrophy, Heymsfield said.

It’s also unclear how to get rid of unwanted muscle fat, Heymsfield said.

“The science is evolving, but I think if you’re losing weight and exercising, I’d say those are two really good ways to reduce it,” Heymsfield said. “There might be some that don’t go away no matter what you do, it might be the genetic part or the part from muscle cell death.”

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A 2021 evidence review a Journal of Applied Physiology found that “exercise can significantly improve muscle quality in populations at risk of developing obesity” by reducing muscle fat content.

This study shows that a CT scan can be a useful tool for many health screenings, including examining adipose tissue, Pickhardt said.

“I can envision a time in the not-too-distant future when this is a planned screening measure,” Pickhardt said. “You can do it with about the same amount of radiation as a normal abdominal X-ray.

“I’m a little hesitant to call it a virtual physical exam, but that’s kind of the concept,” Pickhardt added.

According to Heymsfield, a CT scan currently appears to be the best way to assess levels of muscle fat. “You can get an estimate with ultrasound, but not with the same accuracy,” he said.

But people shouldn’t actively worry about whether their muscles are fat because the science about it is so new, he added.

“I think what’s going to happen now is that as AI and other analytics become ubiquitous, radiologists will automatically get that data back when they’re doing an abdominal CT scan,” Heymsfield said. “As a result, people start saying, ‘Wait a minute, what do I do with this?’ The answer is that if you’re overweight or undertrained, those are two things you can easily do.”

More information

The American Council on Exercise is more concerned with fat and exercise.

SOURCES: Perry Pickhardt, MD, Chief of Gastrointestinal Imaging, University of Wisconsin School of Medicine and Public Health; Steven Heymsfield, MD, professor, metabolism and body composition, Louisiana State University Pennington Biomedical Research Center; Angela Tong, MD, Clinical Assistant Professor, Radiology, New York University Grossman School of Medicine; RadiologyMay 16, 2023

Source: https://www.webmd.com/obesity/news/20230519/fat-growing-around-muscles-could-be-a-silent-killer?src=RSS_PUBLIC