Ultra-Processed Food Intake Associated with Decline in Muscle Quality, Study Finds

What if junk food isn't just adding fat to your waist, but also silently weakening your muscles?

A new study published in Radiology suggests that diets high in ultra-processed foods (UPFs) may be linked to poorer muscle quality, particularly in people at risk of knee osteoarthritis. These findings highlight a lesser-known effect of diet—how it may influence not just body weight, but the health of muscles themselves.

Researchers analyzed MRI scans of 615 adults and found that those who consumed more UPFs had greater fat infiltration in their thigh muscles. In simple terms, healthy muscle tissue was increasingly replaced by fat—a change that can reduce strength and physical function over time. This association remained significant even after accounting for body mass index (BMI), and became even stronger when abdominal fat (waist size) was considered.

UPFs include packaged snacks, sugary drinks, instant meals, and processed meats—foods typically high in salt, sugar, unhealthy fats, and additives. These foods often replace more nutritious options, leading to lower intake of protein and essential nutrients that muscles need to stay strong and functional.

The study focused on individuals already at risk of knee osteoarthritis, a condition where joint damage can be worsened by weak muscles and excess body fat. Interestingly, the link between UPF intake and muscle fat was consistent across both men and women, and followed a clear pattern: the more UPFs in the diet, the higher the fat infiltration in muscles.

One key takeaway is that where fat is stored in the body matters. Central obesity—fat around the abdomen—appeared to play a stronger role than overall weight, suggesting that diet quality and fat distribution together may impact muscle health.

Improving diet quality—by reducing ultra-processed foods and focusing on whole, nutrient-rich options—could be a simple yet powerful step toward protecting both muscle and joint health over time.

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