A negative side effect of ultra-processed foods you haven't thought about

It's known that eating high levels of ultra-processed food is associated with negative health outcomes, but a new study is looking at an underexplored impact: muscle health.

In the study, published April 14 in Radiology, researchers found high ultra-processed food consumption in individuals at risk for knee osteoarthritis was associated with worse muscle quality due to higher fat, regardless of sex.

Ultra-processed foods, or UPFs, are factory-made formulations produced largely from refined ingredients, additives (including colorings and preservatives) and little-to-no whole foods. Using artificial flavors and sweeteners, these foods are designed for more palatable tastes and longer shelf life. They're typically higher in sugar, salt and unhealthy fats and devoid of nutrients and fiber.

For example, ingesting UPFs − including packaged meats like hot dogs and bologna − has been associated with more than 30 health conditions, including Type 2 diabetes, heart diseases, mental health disorders and obesity.

The study used thigh MRI scans to assess muscle fat content in 615 participants with an average age of 60, a population at risk for developing the condition.

Knee osteoarthritis is a "degenerative condition in which the cartilage in your joint slowly breaks down," the Cleveland Clinic explains. The condition is also "among the most disabling and costly diseases worldwide," the authors write, adding that obesity is a well-recognized risk factor.

While treatment can help manage symptoms of stiffness, pain and reduced mobility, according to the Cleveland Clinic, knee replacement surgery is often recommended when it becomes severe.

Despite some limitations – including the results not being fully generalizable outside the studied age range and the potential lack of some factors that influence health – the authors noted the study provides "valuable evidence linking ultra-processed food consumption to poor muscle quality, characterized by higher fat content."