A study involving 615 adults at risk for knee osteoarthritis found that a higher intake of ultra-processed foods is associated with increased fat deposits within thigh muscles, as revealed by MRI scans. The research, published in April in the journal Radiology and recirculated in a September ScienceDaily summary, highlights a correlation rather than proving that ultra-processed foods directly cause these changes in muscle fat.
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Researchers accounted for factors such as calorie intake and physical activity, underscoring the significance of thigh muscle quality in supporting and stabilizing the knee. Previous studies have linked declines in such muscle quality to the development and progression of knee osteoarthritis, especially in individuals in their 50s and 60s.
The research distinguishes between subcutaneous fat, which lies just beneath the skin, and intramuscular fat that accumulates within muscle tissue. This intramuscular fat appears as streaks of fat in muscle fibers on MRI scans. Researchers classified these streaks using the Goutallier scale, which ranges from 0 (no fatty streaks) to 4 (more than half fatty signal).
Participants in the study averaged about 60 years old, with a mean body mass index of 27, categorizing them as overweight. On average, ultra-processed foods constituted 41.4% of their diet, including packaged snacks, sugary drinks, breakfast cereals, frozen meals, and processed meats.
Dr. Zehra Akkaya of the University of California, San Francisco, emphasized the research's implications for nutrition's role in muscle quality concerning knee osteoarthritis. However, she noted that the study design—a cross-sectional secondary analysis—limits its findings. Participants reported their diets over the previous year, which can introduce bias from memory recall.
The study evaluated baseline data from the Osteoarthritis Initiative, a national research effort sponsored by the National Institutes of Health, which enrolled adults aged 45 to 79 at four clinical centers. While the results are especially relevant to adults over 50 or those with a family history of knee issues, significant limitations exist in generalizing the findings to all U.S. populations.
For practical measures, experts suggest gradually replacing some ultra-processed foods with whole or minimally processed options and incorporating strength training for thigh muscles. Individuals with specific health conditions, such as diabetes or kidney disease, should confer with healthcare providers before making dietary changes. Affordable substitutes for minimally processed staples include beans, oats, and frozen vegetables.
Future research will aim to follow participants over time to determine if reducing ultra-processed food consumption can impact muscle fat or knee health.