A new study reveals that a diet rich in ultra-processed foods is linked to increased fat accumulation in thigh muscles, independent of calorie intake or physical activity levels. This buildup of intramuscular fat in the thighs may also heighten the risk of developing knee osteoarthritis.
A recent study presented at the annual meeting of the Radiological Society of North America (RSNA) indicates that a diet high in ultra-processed foods correlates with elevated fat levels stored in thigh muscles, irrespective of caloric consumption or physical exercise. Additionally, increased intramuscular fat in these areas may pose a greater risk for knee osteoarthritis.
In contemporary diets, the use of natural and minimally processed ingredients has declined, often being substituted with industrially processed items that are artificially flavored, colored, or chemically modified.
Examples of ultra-processed foods include breakfast cereals, margarines, packaged snacks, hot dogs, soft drinks, energy drinks, candies, desserts, frozen pizzas, ready-to-eat meals, and mass-produced bread and buns among others, which often contain synthesized ingredients.
These types of foods are typically designed for longer shelf life and increased appeal, as they are convenient and combined with sugar, fat, salt, and carbohydrates, all of which engage the brain’s reward system, making it challenging to stop consumption once started.
Researchers conducted this study to explore the relationship between the intake of ultra-processed foods and the presence of intramuscular fat in the thigh region.
“This study is unique as it examines how diet quality, particularly the consumption of ultra-processed foods, affects the amount of intramuscular fat in thigh muscles as assessed through MRI,” explained Zehra Akkaya, M.D., who led the research and is a former Fulbright Scholar at the University of California, San Francisco. “This is the first imaging study to investigate the connection between MRI-based measurements of skeletal muscle quality and dietary quality.”
The research team evaluated data from 666 participants in the Osteoarthritis Initiative who showed no signs of osteoarthritis on imaging. This initiative, backed by the National Institutes of Health, aims to deepen the understanding of how to prevent and manage knee osteoarthritis.
“Prior research from our team and others has indicated that both quantitative and functional decline in thigh muscles may be related to the onset and worsening of knee osteoarthritis,” commented Dr. Akkaya. “This decline can be observed in MRI scans as fatty degeneration of the muscle, where fat begins to replace muscle fibers.”
The sample included 666 participants (455 men and 211 women) with an average age of 60 years. Most participants were classified as overweight, with an average body mass index (BMI) of 27. Notably, around 40% of their dietary intake over the past year consisted of ultra-processed foods.
The investigators discovered a direct correlation: increased consumption of ultra-processed foods was associated with higher levels of intramuscular fat in the thigh muscles, regardless of overall caloric intake.
“In a population of adults at risk of, but not yet affected by, knee or hip osteoarthritis, the intake of ultra-processed foods is associated with elevated fat levels in the thigh muscles,” Dr. Akkaya stated. “These findings remained consistent, regardless of energy consumption, BMI, demographic factors, or activity levels.”
Dr. Akkaya emphasized the importance of targeting modifiable lifestyle factors—primarily focusing on obesity prevention through a nutritious diet and regular exercise—as the primary strategy for managing knee osteoarthritis.
“Osteoarthritis is a growing global health concern with significant costs, being the main contributor to non-cancer-related healthcare expenses in the U.S. and worldwide,” Dr. Akkaya noted. “Since this condition is closely linked to obesity and poor lifestyle habits, there are opportunities for effective lifestyle changes and management of the disease.”
This research sheds light on how diet, particularly the consumption of ultra-processed foods, can influence muscle composition, offering critical insights into how dietary choices affect muscle health.
“Understanding this connection could have important clinical implications, revealing a new viewpoint on the impact of diet quality on musculoskeletal health,” Dr. Akkaya concluded.
Co-authors of the study include Gabby B. Joseph, Ph.D., Katharina Ziegeler, M.D., Wynton M. Sims, John A. Lynch, Ph.D., and Thomas M. Link, M.D., Ph.D.
