A diet high in ultra-processed foods is associated with higher amounts of fat stored inside thigh muscles, regardless of the amount of calories consumed or level of physical activity, according to a study presented at the annual meeting of the Radiological Society of North America (RSNA).

“The novelty of this study is that it investigates the impact of diet quality, specifically the role of ultra-processed foods in relation to intramuscular fat in the thigh muscles assessed by MRI,” said author Zehra Akkaya, M.D., researcher and former Fulbright Scholar in the Department of Radiology and Biomedical Imaging at the University of California, San Francisco. “This is the first imaging study looking into the relationship between MRI-based skeletal muscle quality and quality of diet.”

Higher amounts of intramuscular fat in the thigh could also increase the risk for knee osteoarthritis, according to the study.

For the study, researchers analyzed data from 666 individuals who participated in the Osteoarthritis Initiative who were not yet affected by osteoarthritis, based on imaging. The Osteoarthritis Initiative is a nationwide research study, sponsored by the National Institutes of Health, that helps researchers better understand how to prevent and treat knee osteoarthritis.

“Research from our group and others has previously shown that quantitative and functional decline in thigh muscles is potentially associated with onset and progression of knee osteoarthritis,” Dr. Akkaya said. “On MRI images, this decline can be seen as fatty degeneration of the muscle, where streaks of fat replace muscle fibers.”

The researchers found that the more ultra-processed foods people consumed, the more intramuscular fat they had in their thigh muscles, regardless of energy (caloric) intake.

“In an adult population at risk for but without knee or hip osteoarthritis, consuming ultra-processed foods is linked to increased fat within the thigh muscles,” Dr. Akkaya said. “These findings held true regardless of dietary energy content, BMI, sociodemographic factors or physical activity levels.”

Targeting modifiable lifestyle factors—mainly prevention of obesity via a healthy, balanced diet and adequate exercise—has been the mainstay of initial management for knee osteoarthritis, Dr. Akkaya noted.

By exploring how ultra-processed food consumption impacts muscle composition, this study provides valuable insights into dietary influences on muscle health, according to Dr. Akkaya.
“Understanding this relationship could have important clinical implications, as it offers a new perspective on how diet quality affects musculoskeletal health,” she said.