Choosing fewer ultra-processed foods could help protect the muscle quality that keeps knees stable, according to new MRI research involving adults at risk for knee osteoarthritis. The study, published in Radiology, found that people who ate more ultra-processed foods carried more fat inside their thigh muscles, even after researchers accounted for total calorie and fat intake, physical activity, and sociodemographic factors. Higher levels of intramuscular fat may weaken support around the knee and potentially raise the risk of developing knee osteoarthritis.
What the MRI Study Measured
Researchers examined data from 615 participants in the Osteoarthritis Initiative, a nationwide research program sponsored by the National Institutes of Health. At the time of analysis, none of the participants showed signs of osteoarthritis on imaging. The group included 275 men and 340 women with an average age of 60 and an average body mass index of 27, placing the typical participant in the overweight range.
Based on dietary information covering the previous year, roughly 41% of the food participants consumed was classified as ultra-processed. The more ultra-processed foods a person reported eating, the more fat researchers detected within the thigh muscles, regardless of total calorie intake.
On MRI, this change appears as fatty degeneration of muscle tissue. Instead of muscle fibers making up the tissue uniformly, streaks of fat begin appearing within the muscle. The study used widely available, non-enhanced MRI, which does not require advanced or costly technology and can be incorporated into standard diagnostic practices.
Why Diet Quality Matters Beyond Calories
The findings suggest that diet quality shapes body composition in ways that weight or calorie counts miss. Addressing obesity has long been a primary treatment for knee osteoarthritis, yet the research suggests dietary quality warrants greater attention.
Managing modifiable lifestyle factors has been central to the early treatment and prevention of knee osteoarthritis, usually through maintaining a healthy weight with a balanced diet and regular exercise. Cutting back on ultra-processed foods may help preserve muscle quality, which could reduce some of the burden associated with knee osteoarthritis.
What Counts as Ultra-Processed Food
They combine sugar, fat, salt, and carbohydrates in ways that trigger the brain’s reward system, driving continued consumption.
- Breakfast cereals
- Margarines and spreads
- Packaged snacks
- Hot dogs
- Soft drinks and energy drinks
- Candies and desserts
- Frozen pizzas
- Ready-to-eat meals
- Mass-produced packaged breads and buns
Over recent decades, diets have shifted away from natural ingredients toward processed foods and beverages.
What This Means for Knee Health
Osteoarthritis is an increasingly prevalent and costly global health issue, constituting one of the largest non-cancer-related health care costs in the United States and worldwide. It is highly linked to obesity and unhealthy lifestyle choices.
While several studies have shown detrimental impacts of ultra-processed foods on various health outcomes, data on the relationship between ultra-processed food and body composition in the context of knee osteoarthritis has been limited. This is the first study assessing ultra-processed food’s impact on thigh muscle composition using MRI. The research provides direct insight into how dietary choices influence muscle health.
FAQ
How do ultra-processed foods affect thigh muscles?
Higher consumption of ultra-processed foods was linked to greater fat buildup inside thigh muscles. On MRI scans, this appears as streaks of fat within the muscle tissue, a pattern called fatty degeneration, instead of uniform muscle fibers.
Does calorie intake explain the link between ultra-processed foods and muscle fat?
No. The association remained even after researchers accounted for total calorie and fat intake, physical activity, and sociodemographic factors. Diet quality appears to influence body composition beyond what calorie intake alone shows.
Who was included in the study?
The study analyzed 615 adults from the Osteoarthritis Initiative who showed no signs of osteoarthritis on imaging at the time. The group included 275 men and 340 women with an average age of 60 and an average BMI of 27.
