Ultra-Processed Food May Be Damaging Your Muscles

Higher levels of ultra-processed food in the diet are associated with more fat in the muscles and a greater risk of conditions like osteoarthritis, recent research has found. "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," said study author Dr. Zehra Akkaya, a researcher at the University of California, San Francisco, in a statement. "These findings held true regardless of dietary energy content, BMI [body mass index], sociodemographic factors or physical activity levels." Ultra-processed food is food that is industrially processed, using artificial additives and refined ingredients to create packaged products sold in stores or foods that use these products as ingredients. They may contain preservatives, thickeners, colorings, flavorings, emulsifiers, and other additives designed to make the food convenient, shelf-stable and highly palatable so we buy and eat more. Ultra-processed food can include obvious junk food, such as chips, crackers and corn-based snacks, but it can also include food not generally considered unhealthy, such as sliced bread and fruit-flavored yogurt.

In recent years, ultra-processed food has been associated with a higher risk of health conditions such as type 2 diabetes, heart disease, obesity and more. Scientists debate whether this is because these foods are very processed or because they are more likely to be of poor nutritional quality, namely high in sugar, fat and salt and low in fiber and essential nutrients. In research that will be presented on Wednesday at a conference of the Radiological Society of North America (RSNA) in Illinois, scientists found a link between eating more of these foods and muscle quality. Specifically, they looked at the amount of fat in thigh muscles, called intramuscular fat, to understand how diet quality affects the risk for osteoarthritis. They also looked at ultra-processed food as an indicator of overall diet quality. Osteoarthritis is the most common form of arthritis, and it causes joint pain, stiffness and swelling that can lead to changes in bones, cartilage and other joint tissues. It is most common in adults over the age of 45, and risk factors include repetitive joint stress or injury, being overweight and being female. "Osteoarthritis is an increasingly prevalent and costly global health issue," said Akkaya. "It is the largest contributor to non-cancer related healthcare costs in the U.S. and around the world. "Research from our group and others has previously shown that quantitative functional decline in thigh muscles is potentially associated with onset and progression of knee arthritis." Having excess fat in muscles is also associated with muscle weakness, poor muscle quality and conditions such as obesity, type 2 diabetes and insulin resistance, in part because it can disrupt how the body processes food. This study analyzed the link between the diets of more than 650 older individuals in the U.S. and intramuscular fat, using information from food questionnaires and MRI scans. On average, participants were 60 years old, were overweight, and ate diets that were 40 percent ultra-processed food, which is less than the U.S. average. Data was taken from the Osteoarthritis Initiative, a nationwide study sponsored by the National Institutes of Health focused on knee osteoarthritis. The scientists found that a higher intake of ultra-processed food was associated with more thigh muscle fat, regardless of how many calories participants ate, how much exercise they did, or how much they weighed. "Understanding this relationship could have important clinical implications, as it offers a new perspective on how diet quality affects musculoskeletal health," said Akkaya. Do you have a tip on a food story that Newsweek should be covering? Is there a nutrition concern that's worrying you? Let us know via science@newsweek.com. We can ask experts for advice, and your story could be featured in Newsweek.