A recent study published in the journal Radiology indicates that high consumption of ultraprocessed foods may adversely affect muscle health. These foods, such as salty snacks, sugary drinks, and fast food, comprise a significant portion of the typical American diet, which already poses known risks for heart health and diabetes. Dr. Thomas Link, senior author of the study and chief of musculoskeletal imaging at the University of California San Francisco, emphasized the less acknowledged effect of diet on musculoskeletal health.
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Muscle fat can manifest in two forms: intermuscular fat, which accumulates between muscles, and intramuscular fat, stored within muscle fibers. Although everyone has some of both types, excess intermuscular fat is seldom found in elite athletes, as noted by Christopher Fry, co-director of the Center for Muscle Biology at the University of Kentucky. He described how athletes utilize the fat in their muscles as energy reserves during intense physical exertion. When these reserves are not engaged, or when a metabolic condition like Type 2 diabetes is present, fat buildup can occur, particularly between muscles.
To investigate the dietary impact on muscular fat, Link and his team analyzed data from 615 participants, averaging 60 years of age, enrolled in the National Institute of Arthritis and Musculoskeletal and Skin Diseases’ Osteoarthritis Initiative. All participants were at risk for knee osteoarthritis, either through obesity, being overweight, or prior knee injuries. Link pointed out that higher levels of intermuscular fat are associated with an increased risk of knee osteoarthritis due to the changes in muscle structure and force exertion.
The research team evaluated participants' body mass index, caloric intake, and dietary habits, alongside MRI scans of their thighs to measure muscle fat content. Findings revealed that about 65% of participants were overweight, and 24% were classified as obese. Intriguingly, the MRI results showed that individuals consuming high quantities of ultraprocessed foods exhibited greater levels of fat within their muscles, irrespective of their BMI, caloric intake, or exercise levels.
Further studies are needed to determine causality regarding ultraprocessed food consumption and intramuscular fat accumulation. Dr. Link noted that while obesity typically correlates with high caloric intake, the effects of ultraprocessed foods extend beyond this.
Essential nutrients for muscle health, such as protein, omega-3 fatty acids, and iron, are often lacking in ultraprocessed foods, which are typically calorie-dense but nutrient-poor. Dr. Tamiko Katsumoto, a clinical associate professor at Stanford University, warned that if ultraprocessed foods contribute to fat build-up in muscles, it can affect muscle function and stability, not just in the legs but in other areas as well.
Prior research established a 1% increase in muscular fat correlates with a 7% rise in cardiovascular disease risk. Increased intramuscular fat has also been linked to a higher risk of Type 2 diabetes. Researchers continue to explore the mechanisms behind these associations, with Dr. Link highlighting the role of inflammation caused by cytokines released from fatty muscles as a potential factor.
Although reversing fat accumulation in muscles is possible through the consumption of whole foods and increased physical activity, Dr. Link and Fry noted that achieving long-term changes requires sustained lifestyle adjustments.