Ultra‑processed foods harm muscles

A diet heavy in ultra-processed foods was linked this week to fattier thigh muscles in adults already at risk for knee osteoarthritis. (rsna.org) The study, published April 14 in *Radiology*, analyzed 615 people in the Osteoarthritis Initiative, a National Institutes of Health-backed research project on knee arthritis. The group included 275 men and 340 women with an average age of 60 and an average body mass index of 27. (rsna.org) Researchers used magnetic resonance imaging, or MRI, scans to measure fat inside the thigh muscles and compared those images with participants’ diets over the prior year. On average, about 41% of the foods participants ate were ultra-processed. (rsna.org) Ultra-processed foods are industrial formulations made with ingredients not commonly used in home kitchens, and the study examples included breakfast cereals, packaged snacks, soft drinks, candies, frozen pizzas and ready-to-eat meals. In the United States, those foods make up about 60% of calories in the average diet, according to NBC News’ report on the study. (rsna.org, nbcnewyork.com) The main finding was not simply about body weight. The link between ultra-processed foods and higher thigh-muscle fat held even after researchers accounted for calorie intake, fat intake, physical activity and sociodemographic factors. (rsna.org, rttnews.com) That matters because muscle fat is different from the fat stored under the skin. NBC News reported that fat can collect as droplets inside muscle fibers or as streaks between muscles, and higher levels between thigh muscles are associated with worse muscle quality and higher knee osteoarthritis risk. (nbcnewyork.com) Senior author Thomas Link of the University of California, San Francisco, said diet’s effect on muscle and joint health is less widely recognized than its effect on heart disease or diabetes. Lead author Zehra Akkaya said the findings suggest diet quality deserves attention alongside weight loss and exercise in efforts to prevent knee osteoarthritis. (nbcnewyork.com, rttnews.com) Outside experts told NBC News the study shows an association, not proof that ultra-processed foods directly caused the muscle changes. Christopher Fry of the University of Kentucky, who was not involved in the research, said fat buildup can alter how thigh muscles generate force and how the knee absorbs that force over time. (nbcnewyork.com) The study did not test whether changing someone’s diet reverses muscle fat or prevents arthritis, so that question is still open. For now, the new evidence adds thigh muscle quality to the list of health measures that may track with how much ultra-processed food people eat. (rsna.org, nbcnewyork.com)