By Dennis Thompson
health day reporter
THURSDAY, May 18, 2023 (HealthDay News) — It’s well known that having belly fat accumulating around your abdominal organs is unhealthy, but there’s a more insidious form of fat that could be even more dangerous. for your health, according to a new study.
Fat seeping into your muscles appears to significantly increase your risk of death, according to findings published May 16 in the journal Radiology.
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, the researchers found.
In comparison, obesity appeared to increase participants’ absolute mortality risk by just 7.6%, according to the results. Fatty liver increased the risk by 8.5% and muscle wasting by 9.7%.
“The signal [for muscle fat risk] was so much stronger for this otherwise healthy cohort,” said lead researcher Dr. Perry Pickhardt, chief of gastrointestinal imaging at the University of Wisconsin School of Medicine and Public Health. “It really stood out as a powerful biomarker beyond the things that I think we all accept as important metrics.
“I think there’s going to be patient profiling where if you line up myosteatosis with very fatty liver or maybe lots of visceral fat, you could be a lot worse than if you only had one or two. “, added Pickhardt. .
Muscle fat is of growing interest in the areas of obesity and diabetes, said Dr. Steven Heymsfield, professor of metabolism and body composition at Louisiana State University’s Pennington Biomedical Research Center.
There’s a small, healthy amount of naturally occurring fat inside every muscle cell that can be used to generate 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 fibers and muscle bundles.
Think of a steak
“If you think about a steak, the marbling in the steak is what we’re dealing with here,” Heymsfield said. “Over the past two decades, it has been shown to be correlated with adverse health effects, as shown in this study.”
The average person carries a few pounds of muscle fat spread throughout their bodies, Heymsfield said. It is more likely to congregate in the legs than in other areas of the body.
Pickhardt and colleagues conducted their study in a group of nearly 9,000 healthy patients who underwent low-dose CT scans for colon cancer screening, a procedure known as virtual colonoscopy, between 2004 and 2016. .
The researchers realized that these CT scans could be useful in assessing other potential health issues, given the vast amount of data the scans gather about a person’s physique.
“When we look at measurements of visceral fat and muscle and aortic calcium or liver or bone marrow fat density, all of those things add up and basically you can end up with this kind of really powerful virtual physical exam, if you will, and just leveraging CTs done for whatever reason,” Pickhardt said.
“We call it ‘opportunistic screening’ for now, because it’s about taking data that was essentially ignored or discarded and exploiting it in new ways,” he added.
So the research team trained an artificial intelligence tool to extract body composition measurements from abdominal CT scans, specifically assessing each person’s belly fat, muscle fat, liver fat and muscle wasting.
Automated software simplified the process. “It would have taken a lifetime to do this with the old ways,” Heymsfield said.
The researchers then followed the participants for an average of nine years to see if any of these measures could be linked to major health problems or premature death.
Not only was muscle fat associated with the highest risk of death, but the association held even after the researchers took into account each person’s BMI (body mass index) – the best measure available for obesity.
Skinny people at risk too
“BMI was actually a very poor predictor and had a very weak signal,” Pickhardt said. “Clearly there are patients who weren’t obese who had this poor muscle measurement. That’s what makes it so important – there are people who are lean in terms of BMI who actually have a worse profile than you think so.
However, this study does not establish a clear causal relationship between muscle fat and the risk of death, noted Dr. Angela Tong, clinical assistant professor of radiology at the University of New York School of Medicine. York.
Muscle fat could be accumulating due to another health condition that is the real risk, said Tong, co-author of an editorial published with the study.
“I think of it more as a sign that maybe something else is going on, maybe something else in your health that’s not allowing you to be as active,” Tong said. “You should look carefully if there are heart problems or diabetes.”
Other studies have linked fatty muscles to poor outcomes. For example, a 2020 evidence review published in Critical reviews in oncology/hematology found that cancer patients diagnosed with myosteatosis had a 75% higher risk of mortality than those without fatty muscles.
How’s it going ?
It’s unclear exactly why your muscles might start piling on fat, Heymsfield said.
“There may be genetic factors involved, and that increases with age, despite your best intentions to lift weights or exercise,” Heymsfield said.
Muscle fat is also known to accumulate if your muscles atrophy, Heymsfield said.
“Let’s say you have a cast on your leg and the muscles atrophy, sometimes those muscle cells are replaced by fat cells,” Heymsfield said. “That’s probably the biggest source of what these investigators found.”
For example, myosteatosis is a hallmark of certain types of muscular dystrophy, Heymsfield said.
It’s also unclear how you can 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 may be some that won’t go away no matter what you do, maybe the genetic part or the part that comes from muscle cell death.”
A review of the 2021 evidence in the Journal of Applied Physiology found that “exercise can significantly improve muscle quality in populations at risk of developing obesity,” leading to a decrease in muscle fat.
This study shows that CT scans could be a useful tool for a variety of health screenings, including for fatty muscles, Pickhardt said.
“I could imagine a time in the not-too-distant future when this would be an intentional screening measure,” Pickhardt said. “You can do this for about the same amount of radiation as a standard abdominal X-ray.
“I’m a bit hesitant to call it a virtual physical exam, but that’s kind of the concept,” Pickhardt added.
Heymsfield said CT scans seem to be the best way to assess muscle fat levels right now. “You could get an estimate with an ultrasound, but not to the same degree of accuracy,” he said.
But people shouldn’t actively worry about whether their muscles are fat, since the science on this is so new, he added.
“I think what’s going to happen now is that AI and other scanning methods are going to become ubiquitous, that radiologists are going to pick up that data automatically right when they’re doing an abdominal CT scan,” said said Heymsfield. “As a result, people are going to start saying, ‘Wait a minute, what do I do about this?’ The answer is if you’re overweight or not exercising enough, those are two things you can easily do in response.”
More information
The American Council on Exercise says more about fat and exercise.
SOURCES: Perry Pickhardt, MD, chief, 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