Ultra‑processed food harms muscle
New research reported this week found diets high in ultra‑processed foods are associated with higher amounts of fat inside thigh muscles, which the authors link to a potential increased risk of knee osteoarthritis. (nbcnews.com) Multiple outlets cite the Radiology/RSNA release describing intramuscular fat and the possible musculoskeletal consequences. (cnn.com) (prweb.com)
A new study tied diets high in ultra-processed foods to more fat embedded inside thigh muscles, a change linked to higher knee osteoarthritis risk. (rsna.org) The research was published April 14 in *Radiology* and analyzed 615 adults in the National Institutes of Health-backed Osteoarthritis Initiative who had no imaging signs of osteoarthritis at the time. Participants averaged 60 years old, had an average body mass index of 27, and got about 41% of their food over the prior year from ultra-processed products. (rsna.org) Researchers found that people who ate more ultra-processed food had more intramuscular fat in the thigh even after accounting for calories, fat intake, physical activity and sociodemographic factors. The lead author, Zehra Akkaya of the University of California, San Francisco, said the study focused on people already considered at risk for knee osteoarthritis. (rsna.org) Muscles can hold fat in two places: tiny droplets inside muscle fibers and thicker streaks between muscle groups. Christopher Fry, a muscle biologist at the University of Kentucky who was not involved in the study, told NBC News that some stored fat is normal, but expanding streaks between muscles are “not going to be good.” (nbcnews.com) That matters at the knee because thigh muscles help stabilize the joint every time a person stands, walks or climbs stairs. NBC News reported that weaker, fattier muscle can change how force moves through the leg and help wear down cartilage, the tissue that cushions the joint. (nbcnews.com) Ultra-processed foods are industrial formulations made with ingredients and additives not usually found in home kitchens, and the study’s examples included packaged snacks, soft drinks, candies, frozen pizzas, ready-to-eat meals and mass-produced breads. The Radiological Society of North America said these foods are designed to be convenient, shelf-stable and highly appealing. (rsna.org) The finding lands as ultra-processed foods make up most calories in the United States diet. The Centers for Disease Control and Prevention reported in August 2025 that ultra-processed foods accounted for 53.0% of calories among adults and 61.9% among children and teens. (cdc.gov) Knee osteoarthritis is already widespread. The World Health Organization said about 528 million people worldwide were living with osteoarthritis in 2019, and knee osteoarthritis accounted for 365 million of those cases. (who.int) The study does not prove that ultra-processed food directly causes muscle fat or knee arthritis, because it was a cross-sectional analysis that measured diet and muscle quality at one point in time. But it adds muscle quality to a list of health concerns already associated with diets built around heavily processed foods. (rsna.org)
