MRI scans of two women’s thighs show what 87 percent ultra-processed food diet does to your muscles, and the images are hard to look at

New MRI scans are revealing what a diet high in ultra-processed foods does to muscle tissue, and the images make the damage impossible to ignore. As highlighted by UNILAD, researchers compared the thigh muscle composition of two women with drastically different diets, producing a stark visual contrast between healthy muscle and fat-infiltrated tissue. The findings, published in the journal Radiology by the Radiological Society of North America, are being described as the first study to assess ultra-processed food’s impact on thigh muscle composition using MRI.

Ultra-processed foods, or UPFs, are not simply foods that have undergone some degree of processing. They are products reinforced with chemical additives, colorings, preservatives, and industrial compounds not found in home cooking, and they typically contain high levels of calories, sugar, fat, and salt. Common examples include cold cereals, soft drinks, potato chips, canned goods, cured meats, and frozen dinners. Dr. Zehra Akkaya, a researcher at the University of California San Francisco Department of Radiology and Biomedical Imaging, noted that over recent decades the use of natural ingredients in diets has steadily given way to industrially processed alternatives, a shift occurring alongside rising rates of obesity and knee osteoarthritis.

The case study at the center of the research compared two women of similar age, body mass index, and physical activity levels. One woman, aged 62, sourced nearly 87 percent of her daily nutrition from UPFs, with her diet consisting of items like cold cereals, chocolate candy bars, and soda. The other, aged 61, drew only 30 percent of her diet from UPFs. Their MRI scans told the difference clearly.

A diet high in ultra-processed foods is rewriting what’s inside your muscles

The 61-year-old with the lower UPF intake showed minimal fat infiltration in her thigh muscles. The 62-year-old with the higher intake exhibited significantly greater “marbling,” a condition in which fat accumulates within muscle fibers and actively replaces healthy tissue. Her Goutallier grade for all thigh muscles summed to 38, compared to 25 for the woman with the lower UPF diet. She also qualified as having abdominal obesity, a key marker of cardiometabolic health.

This fat accumulation within muscle tissue is a condition called myosteatosis. People with higher levels of intramuscular fat tend to experience elevated rates of insulin resistance, metabolic syndrome, and chronic inflammation. Higher muscle fat is also directly linked to increased risk of metabolic disease and makes everyday physical activity more difficult, which can accelerate muscle loss over time.

To examine the connection more broadly, researchers drew on data from the Osteoarthritis Initiative, a National Institutes of Health-sponsored study tracking individuals at risk for knee arthritis. They focused on 615 participants without existing arthritis, chronic disease, or joint pain, each of whom completed a detailed dietary questionnaire covering the past year. Amid a broader public conversation about diet and chronic illness, a Nevada woman who collected nearly $20K falsely claiming cancer recently highlighted how far health deception can reach. Every participant in the research study also underwent an MRI scan of their thighs, with fat infiltration graded across muscle groups including the hamstrings, quadriceps, and inner thighs on a scale from zero to four.

The results were consistent across all muscle groups studied: as UPF consumption increased, intramuscular fat levels rose. Crucially, this correlation held regardless of calorie or fat intake, physical activity, or sociodemographic factors, indicating that dietary quality, not just quantity, is a meaningful factor in muscle composition. Dr. Akkaya stated that the research “underscores the vital role of nutrition in muscle quality in the context of knee osteoarthritis.” The study, which drew public health attention not unlike the concern around the measles surge and vaccine messaging, also noted that the non-enhanced MRI method used is accessible and practical for routine clinical use.

Dr. Akkaya concluded that while addressing obesity remains a primary objective in treating knee osteoarthritis, the findings “emphasize that dietary quality warrants greater attention, and weight loss regimens should take into account diet quality beyond caloric restriction and exercise.”