Ultra-Processed Foods Linked to Fat Accumulation in Thigh Muscles

A recent study involving 615 adults has identified a connection between high consumption of ultra-processed foods and greater fat deposits within thigh muscles. This accumulation of intramuscular fat could potentially raise the likelihood of developing knee osteoarthritis, a condition affecting joint health.

Researchers examined participants from the Osteoarthritis Initiative, a nationwide project funded by the National Institutes of Health aimed at understanding knee osteoarthritis prevention and treatment. The individuals, averaging 60 years in age and with a mean body mass index of 27, had no osteoarthritis signs on initial imaging.

Study Design and Dietary Assessment

The investigation focused on the dietary habits of the participants over the previous year, finding that about 41% of their food intake consisted of ultra-processed items. These foods are characterized by their long shelf life, convenience, and combinations of sugar, fat, salt, and refined carbohydrates designed to enhance flavor and encourage overeating.

Examples of such products include packaged snacks, soft drinks, frozen meals, breakfast cereals, and mass-produced breads containing synthetic ingredients. The study controlled for total calorie and fat intake, physical activity levels, and sociodemographic factors to isolate the impact of ultra-processed food consumption on muscle fat.

MRI Analysis Reveals Muscle Fat Infiltration

Magnetic resonance imaging (MRI) scans were used to detect fatty degeneration within thigh muscles, where fat gradually replaces muscle fibers. The use of non-enhanced MRI technology allowed for accessible and practical assessment without requiring advanced or costly equipment.

“These MRIs do not require advanced or costly technology, which means they can be easily incorporated into standard diagnostic practices,” explained Zehra Akkaya, M.D., lead author and researcher at the University of California, San Francisco.

The findings demonstrated that higher intake of ultra-processed foods correlated with increased intramuscular fat, independent of total calorie consumption. This suggests that diet quality plays a significant role in muscle health beyond caloric intake alone.

Implications for Knee Osteoarthritis and Nutrition

Knee osteoarthritis, a prevalent and costly health issue worldwide, is strongly associated with obesity and lifestyle factors. The study highlights the importance of considering dietary quality in managing muscle composition and osteoarthritis risk.

“Addressing obesity is a primary objective and frontline treatment for knee osteoarthritis, yet the findings from this research emphasize that dietary quality warrants greater attention,” Dr. Akkaya stated.

Reducing consumption of ultra-processed foods may help preserve muscle quality and lessen the burden of knee osteoarthritis. The research team emphasized that weight loss strategies should incorporate dietary improvements alongside exercise and caloric management.

Novel Insights and Future Directions

This investigation represents the first to assess the impact of ultra-processed food intake on thigh muscle composition using MRI. By shedding light on how these foods influence muscle fat infiltration, the study provides valuable insights into the role of nutrition in musculoskeletal health.

“This is the first study assessing ultra-processed food’s impact on thigh muscle composition using MRI,” Dr. Akkaya noted. “By exploring how ultra-processed food consumption impacts muscle composition, this study provides valuable insights into dietary influences on muscle health.”

The full study, titled “Ultra-processed Foods and Muscle Fat Infiltration at Thigh MRI: Data from the Osteoarthritis Initiative,” was published on April 14, 2026, in the journal Radiology.