- A new MRI study found that higher intake of ultra-processed foods was linked to more fat infiltration in thigh muscles in adults at risk of knee osteoarthritis.
- The association remained after accounting for BMI, suggesting diet quality may matter for muscle health as well as body weight.
- The study was cross-sectional, so it cannot prove that ultra-processed foods caused the poorer muscle quality.
Researchers analysed MRI and diet data from 615 adults in the Osteoarthritis Initiative.
These were people at risk of knee osteoarthritis, but without established radiographic disease or major comorbidities.
The researchers wanted to know whether diets higher in ultra-processed foods were linked to worse muscle composition.
They focused on fat infiltration in thigh muscles.
- Ultra-processed foods linked to lower fertility and slower early embryo development
- Ultra-processed foods in preschool years associated with behavioural difficulties
That is a useful marker because muscle can look normal in size while still becoming poorer in quality if it contains more fat.
The study found that higher ultra-processed food intake was associated with greater fat infiltration across the thigh muscles.
The link remained even after adjusting for BMI.
In fact, the associations were stronger when the researchers adjusted for abdominal circumference instead.
That suggests body fat distribution may be part of the story too.
The result fits with wider concerns about ultra-processed foods.
- Ultra-processed foods engineered to be addictive
- High intake of ultra-processed foods linked to higher death risk in cancer survivors
These diets are often high in salt, sugar, fat and additives, while crowding out nutrient-dense foods that support muscle health, including sources of protein and key micronutrients.
The study cannot tell us whether ultra-processed foods directly damaged muscle.
It also cannot rule out all other explanations.
But it does add another piece to the puzzle.
Poor diet quality may be affecting not just weight and metabolic health, but the quality of muscle tissue itself.
That could matter a great deal as people age, especially when mobility and joint health are already under strain.
