Ultra-Processed Foods May Promote Muscle Fat and Raise Knee Osteoarthritis Risk: Study

Ultra-processed foods may be linked to higher levels of fat inside thigh muscles, potentially affecting knee health, according to new research, raising questions about whether diet quality may affect joint health through changes in muscle tissue.

Published in Radiology, the study analysed 615 people from the Osteoarthritis Initiative who had no imaging evidence of knee osteoarthritis. Participants had an average age of 60 years, and about 41% of the food they consumed was classified as ultra-processed.

Researchers examined dietary information and used MRI scans to assess thigh muscle composition. They found that people who reported eating more ultra-processed foods tended to have more intramuscular fat, regardless of their total calorie intake, physical activity and sociodemographic factors.

Intramuscular fat refers to fat stored within muscle tissue. On MRI scans, it can appear as fatty streaks replacing some of the normal muscle fibres. Changes in muscle composition may be relevant to knee osteoarthritis because thigh muscles help support and stabilise the knee.

The findings suggest diet quality may influence muscle health beyond body weight and calorie intake. Reducing ultra-processed foods could potentially help preserve muscle quality.

However, the study found an association and cannot prove that ultra-processed foods cause fat to accumulate inside muscles or directly increase osteoarthritis risk. Dietary intake was based on participants’ reports, which may also introduce measurement errors. Further research is needed to determine whether these muscle changes predict future disease.

The researchers said non-enhanced MRI could offer a practical way to study muscle composition because it does not require advanced imaging technology.

Overall, the findings suggest that diet quality may be an important factor in muscle health and knee osteoarthritis research, alongside healthy weight management, balanced nutrition and regular physical activity, rather than calorie restriction alone only.

REFERENCE: Zehra Akkaya, et al.; Ultra-processed Foods and Muscle Fat Infiltration at Thigh MRI: Data from the Osteoarthritis Initiative. Radiology, 2026; 319 (1) DOI: 10.1148/radiol.251129