Ultra-Processed Foods Tied To Hidden Muscle Fat, Raising Osteoarthritis Risk, Study Warns

A growing body of scientific evidence is raising fresh concerns over the health impact of ultra-processed foods, with a new study warning that such diets may silently damage muscle quality and increase the risk of knee osteoarthritis—even among people who are not obese or physically inactive.

Knee osteoarthritis, a progressive degenerative condition marked by the breakdown of cartilage, is already a leading cause of pain, stiffness, and disability, particularly among India’s aging population. Experts say the latest findings add a new dimension to the disease by linking it directly to dietary quality.

Published in Radiology, a journal of the Radiological Society of North America (RSNA), the study found that higher consumption of ultra-processed foods is associated with increased fat accumulation within thigh muscles. This condition, known as intramuscular fat infiltration, weakens muscle strength and may place additional stress on joints, accelerating the onset of osteoarthritis.

Significantly, the association held true irrespective of calorie intake, fat consumption, physical activity, or socioeconomic factors—suggesting that what people eat may matter more than how much they eat.

Ultra-processed foods—now a staple in many urban Indian diets—include packaged snacks, sugary drinks, ready-to-eat meals, processed meats, frozen foods, and mass-produced baked items. These products are typically high in refined sugars, unhealthy fats, salt, and artificial additives, designed to enhance taste and shelf life while encouraging repeat consumption.

“Over the past decades, the use of natural ingredients has steadily diminished, replaced by industrially processed and chemically altered foods,” said lead author Dr. Zehra Akkaya of the University of California, San Francisco, pointing to a broader global dietary shift.

The study analyzed 615 participants from the Osteoarthritis Initiative, a long-term research program supported by the US National Institutes of Health. None had osteoarthritis at the outset, allowing researchers to track early structural changes.

Participants, with an average age of 60 and a mean body mass index of 27, derived nearly 41% of their annual diet from ultra-processed foods. MRI scans revealed that higher intake correlated with greater fat infiltration in thigh muscles—an early marker of muscle degeneration where healthy fibers are replaced by fat.

Researchers noted that this deterioration can reduce muscle efficiency and stability, placing added strain on knee joints over time.

“This research underscores the vital role of nutrition in muscle quality,” Dr. Akkaya said, adding that prevention strategies must move beyond calorie restriction and incorporate dietary quality.

Public health experts say the findings are particularly relevant for India, where ultra-processed foods are rapidly replacing traditional diets rich in whole grains, pulses, and fresh produce. The shift, driven by urbanization, convenience, and aggressive marketing, has already been linked to rising rates of obesity, diabetes, and heart disease.

Commenting on the study, Dr. Arun Gupta, pediatrician and convener of Nutrition Advocacy in Public Interest (NAPi), said the findings reinforce concerns about the harmful impact of ultra-processed diets.

“The study clearly shows that poor diet quality is associated with greater thigh muscle fat infiltration, independent of calorie intake or socioeconomic factors,” he said. “This dismantles the argument that simply reducing calories in ultra-processed foods is enough. It is the products themselves that are problematic.”

Dr. Gupta pointed out that such foods are often nutritionally poor, particularly in protein, which is essential for maintaining muscle health. He added that the evidence linking ultra-processed foods to disease is already substantial.

“We now have global data linking these foods to multiple conditions, including obesity, diabetes, heart disease, depression, and cancer. There are controlled trials showing they lead to overeating, and neuroimaging studies demonstrating how they affect the brain’s reward system,” he said.

Calling for urgent policy action, he added, “How much more evidence do we need? India cannot wait. We need warning labels, restrictions on marketing, and stronger regulation of ultra-processed foods.”

Experts note that while further research is needed to establish direct causality, the study adds to a growing consensus that diet quality is a critical, yet often overlooked, factor in long-term health.

For a country like India—facing a dual burden of malnutrition and rising lifestyle diseases—the findings serve as a stark reminder that the consequences of dietary change may extend beyond weight gain, quietly affecting muscle health, mobility, and quality of life in later years.