Study Links Ultraprocessed Food Consumption to Reduced Muscle Health

More than half of the calories Americans consume come from ultraprocessed foods — and a mounting stack of research suggests those calories may be weakening the very muscles that keep people mobile, independent, and alive. A study published in the journal Radiology in late 2024 found that people who ate more ultraprocessed foods had significantly more fat infiltrating their thigh muscles, regardless of how many calories they consumed or how much they exercised [1]. The finding adds to a body of evidence spanning systematic reviews, prospective cohort studies, and cross-sectional analyses that all point in the same direction: what food is made of may matter less than what has been done to it.

What the Studies Actually Measured

The Radiology study analyzed data from 666 participants (455 men, 211 women, average age 60) enrolled in the Osteoarthritis Initiative, a National Institutes of Health–sponsored research program. Researchers used MRI scans to assess intramuscular fat in thigh muscles, grading it on a semi-quantitative five-level scale called the Goutallier grade. Dietary intake was measured through food-frequency questionnaires, with approximately 40% of participants' dietary intake classified as ultraprocessed [1][2].

The central finding: for each standard-deviation increase in ultraprocessed food consumption, intramuscular fat scores rose by nearly one full Goutallier grade (p = 0.021). This relationship held after adjusting for total caloric intake, BMI, sociodemographic factors, and physical activity levels [2]. Prior research has shown that each 1% increase in muscular fat raises cardiovascular disease risk by 7%, and that higher intramuscular fat in the thigh increases osteoarthritis risk [1].

This is not an isolated result. A systematic review and dose–response meta-analysis published in the Journal of Health, Population and Nutrition in 2025 examined 43 studies and found a dose-dependent relationship between ultraprocessed food intake and reduced grip strength, slower gait speed, elevated inflammatory markers (C-reactive protein, IL-6, TNF-α), and lower muscle mass indices [4]. A prospective analysis of the Tianjin Chronic Low-Grade Systemic Inflammation and Health (TCLSIH) study found that a 10% increase in dietary ultraprocessed food calories was associated with a 0.37-kg decrease in annual grip strength [5]. A cross-sectional NHANES study found that adults aged 20–59 in the highest quintile of ultraprocessed food intake had a 60% increased risk of low muscle mass compared to the lowest quintile [3].

For context, physical inactivity is estimated to accelerate muscle mass loss by 3–5% per decade after age 30, with grip strength declines of roughly 1–2 kg per year in sedentary older adults. The ultraprocessed food effect sizes documented here — particularly the 0.37-kg annual grip strength decline per 10% increase in ultraprocessed food calories — represent a meaningful fraction of the loss attributed to inactivity alone [4][5].

Defining "Ultraprocessed": The NOVA Framework and Its Critics

Every study discussed here relies on the NOVA classification system, developed by researchers at the University of São Paulo, to categorize foods into four groups based on the extent of industrial processing. Group 4 — ultraprocessed foods — includes products made with ingredients rarely found in home kitchens: hydrogenated oils, modified starches, protein isolates, emulsifiers, flavor enhancers, and artificial colorings [6].

In practice, this category sweeps in a wide range of products: packaged snacks, sweetened beverages, instant noodles, reconstituted meat products, and mass-produced bread, but also some whole-grain breads, flavored yogurts, and plant-based milks [7]. The top sources of ultraprocessed food calories in the U.S. are sandwiches (including burgers) at 8.6% of adult ultraprocessed calories, sweet bakery products (5.2%), sweetened beverages (4.4%), savory snacks (3.4%), and breads, rolls, and tortillas (3.1%) [6].

Critics argue this classification lacks scientific precision. A 2021 review in Trends in Food Science & Technology noted that NOVA's criteria are based more on formulation — the addition of sugar, salt, and industrial-use ingredients — than on actual processing techniques, leading to inconsistent categorization [8]. The International Union of Food Science and Technology has pointed out that over 50% of foods in the base of the Mediterranean diet pyramid can be classified as ultraprocessed under NOVA, which undermines the system's discriminatory power [8][9]. Some researchers have called NOVA an oversimplification that dismisses the proven benefits of diets that include fortified and processed foods chosen in appropriate proportions [8].

These criticisms matter because if the classification is too blunt, the observed associations between "ultraprocessed food" and muscle loss could partly reflect confounding by overall diet quality rather than something specific to industrial processing.

The Biological Case: How Processing Might Damage Muscles

Researchers have proposed several mechanisms through which ultraprocessed foods could impair muscle health. The hypotheses are not mutually exclusive, and they vary considerably in the strength of their supporting evidence.

Nutrient displacement. The most straightforward explanation is that ultraprocessed foods crowd out protein, fiber, and micronutrients critical for muscle maintenance — including vitamins A, C, and E, along with zinc, selenium, magnesium, and iron [3][4]. This mechanism has the broadest observational support, but it raises a question: if the issue is simply inadequate protein, then the problem is not ultraprocessing per se but poor diet composition, which could be addressed without eliminating all industrially processed foods.

Amino acid bioavailability. Food processing at high temperatures, particularly in the presence of reducing sugars, triggers Maillard reactions that modify amino acid side chains and reduce their bioavailability. Research published in Nutrition Research Reviews found that glycation of 20% and 50% reduced postprandial plasma lysine availability by 35% and 92%, respectively [10]. This suggests that even when ultraprocessed foods contain nominally adequate protein, the body may absorb less of it. However, the extent to which this occurs with typical commercial products — as opposed to extreme laboratory conditions — remains unclear.

Systemic inflammation. The meta-analysis in Journal of Health, Population and Nutrition found elevated inflammatory markers (CRP, IL-6, TNF-α) in high ultraprocessed food consumers [4]. Chronic low-grade inflammation is an established driver of sarcopenia — the age-related loss of muscle mass and function. Whether specific additives (emulsifiers, preservatives) directly trigger inflammation, or whether the inflammatory response is secondary to metabolic dysfunction from excess sugar and refined carbohydrates, is an active area of investigation.

Intramuscular fat infiltration. The Radiology study suggests a specific pathway where ultraprocessed foods promote fat deposition within muscle fibers, replacing functional contractile tissue [1][2]. This is distinct from overall body fat accumulation and could explain why the association persists after controlling for BMI. The mechanism driving this selective fat deposition is not yet established.

Of these, nutrient displacement has the strongest epidemiological support, amino acid bioavailability has direct experimental evidence at extreme processing levels, and the inflammation and fat-infiltration pathways remain largely correlational.

Study Design: How Strong Is the Evidence?

The Radiology study is a cross-sectional analysis — it measured diet and muscle fat at a single point in time, which means it cannot establish that ultraprocessed food consumption caused the observed fat infiltration [1][2]. The same limitation applies to the NHANES analysis linking ultraprocessed food intake to low muscle mass [3].

The TCLSIH study used a prospective cohort design, following participants over time, which strengthens the case for a temporal relationship between ultraprocessed food consumption and grip strength decline [5]. The 2025 systematic review encompassed 43 studies across multiple designs and populations, and the consistency of the association across studies is notable [4].

Confounders controlled for across these studies include total caloric intake, physical activity, smoking status, BMI, age, sex, and socioeconomic status. The Radiology study specifically adjusted for energy intake and activity levels, and found the association persisted [2].

Residual confounding remains a real concern. People who eat more ultraprocessed food may differ from those who eat less in ways that are difficult to measure: sleep quality, stress levels, overall health literacy, medication use, or unmeasured aspects of physical activity. No randomized controlled trial has yet tested whether reducing ultraprocessed food intake improves muscle health outcomes, which means the evidence, while consistent and biologically plausible, does not yet meet the threshold for established causation.

The Steelman Case for Skepticism

Several nutrition researchers have raised legitimate concerns about the strength of these conclusions.

An umbrella review of meta-analyses assessing ultraprocessed food and health outcomes found that the credibility of the evidence was rated low for most outcomes, with only moderate-grade evidence for a 2% increase in all-cause mortality and 12% increased risk of type 2 diabetes [11]. Muscle-specific outcomes were not among the endpoints with the strongest evidence base.

A 2025 commentary in Nature Medicine raised concerns about conclusions drawn from ultraprocessed food research more broadly, noting that the NOVA system's imprecision makes it difficult to distinguish between truly harmful industrial processes and benign ones [12]. The American Heart Association's 2024 science advisory acknowledged associations between ultraprocessed food intake and cardiometabolic health but stopped short of recommending ultraprocessed food restrictions, citing the need for more rigorous study designs [13].

The core skeptical argument is not that ultraprocessed foods are healthy, but that the observed associations may be driven by well-known risk factors — excess sugar, sodium, saturated fat, and caloric surplus — rather than by anything unique to industrial processing. If so, the policy response should focus on nutrient composition rather than processing level.

Who Is Most Exposed — and Most Vulnerable

According to CDC data from 2021–2023, ultraprocessed foods account for 55% of total calories consumed by Americans aged one year and older. Youth aged 1–18 consume a higher share (61.9%) than adults (53%) [6].

Source: CDC/NCHS Data Brief No. 536

Data as of Aug 7, 2025CSV

Income shapes consumption patterns. Adults with family incomes below 130% of the federal poverty level get 54.7% of their calories from ultraprocessed foods, compared with 50.4% for those at 350% or above [6]. These are the same populations at elevated risk for sarcopenia due to lower rates of physical activity, reduced access to healthcare, and higher rates of chronic disease.

Racial and ethnic disparities compound the issue. Non-Hispanic Black adults and Hispanic adults are disproportionately represented in lower-income brackets and in food-insecure households, where ultraprocessed foods serve as a primary source of affordable calories [14]. A study in Public Health Nutrition found that SNAP participants consumed significantly more ultraprocessed food than non-participants, driven in part by the relative affordability and shelf stability of these products [14].

The overlap between high-ultraprocessed-food consumers and populations already at greatest risk for muscle loss creates a concerning feedback loop: the people least able to afford alternatives are the ones most exposed to the potential harm.

The Cost Problem: Who Pays for a Processed-Food Pivot?

Ultraprocessed foods cost approximately $0.55 per 100 calories, compared with $1.45 for minimally processed foods — a nearly threefold difference [15].

Source: Johns Hopkins Bloomberg School of Public Health

Data as of Jan 1, 2025CSV

This price gap is not trivial. For a household consuming 2,000 calories per day, shifting from a diet where 55% of calories come from ultraprocessed food to one where only 20% do would increase daily food costs by roughly $3.50 to $5.00, or $105 to $150 per month. For a family of four on SNAP benefits — which averaged $6.20 per person per day in fiscal year 2024 — that increase could consume most or all of the household food budget [14][15].

Research published in the American Journal of Preventive Medicine in 2024 modeled the effects of taxing ultraprocessed foods while subsidizing minimally processed alternatives for low-income households. The authors found that combined fiscal policies could shift purchasing behavior at relatively low federal cost [16]. But absent such policies, telling food-insecure households to eat fewer ultraprocessed foods amounts to telling them to spend money they do not have.

Time costs compound financial ones. Ultraprocessed foods require less preparation — often just reheating — while minimally processed meals require shopping for fresh ingredients, cooking from scratch, and managing perishability. For working households with limited time and kitchen infrastructure, these barriers are not theoretical [15].

Global Trends: A Rising Tide of Ultraprocessing

The United States is not an outlier. Global ultraprocessed food consumption has risen sharply over two decades, driven by urbanization, marketing, and the expansion of supermarket supply chains into low- and middle-income countries [17].

In the U.S., the share of calories from ultraprocessed food among youth rose from 61.4% in 1999 to 67.0% in 2018, before declining modestly to 61.9% by 2021–2023 [6][18]. Among adults, the share hovered around 55–56% from 2003 to 2018, then fell slightly to 53% by 2021–2023 [6]. These declines are statistically significant but small in absolute terms.

By product category, snacks and desserts contribute approximately 33% of energy from ultraprocessed foods, frozen and shelf-stable ready meals account for 16%, and sweetened beverages comprise about 15% [17]. Among youth, ready-to-heat mixed dishes saw the largest growth — from 2.2% of ultraprocessed food calories in 1999 to 11.2% in 2018 — while sugar-sweetened beverage consumption roughly halved over the same period [18].

Source: OpenAlex

Data as of Jan 1, 2026CSV

Academic interest has tracked with public concern. Publications on ultraprocessed food and muscle health indexed in OpenAlex grew from roughly 1,000 per year in 2011 to over 8,500 in 2024, reflecting both expanded research funding and rising media attention.

What Comes Next

The research reviewed here is consistent, biologically plausible, and supported by multiple study designs across diverse populations. But it is not yet definitive. The field needs randomized controlled trials that test whether reducing ultraprocessed food intake — while holding total caloric and protein intake constant — improves objective measures of muscle health like grip strength, lean mass on DEXA scans, and gait speed.

Until that evidence arrives, the practical takeaway is limited but not empty. People concerned about muscle health have more reason to scrutinize the composition of their diet, not just its macronutrient totals. And policymakers should recognize that any public health guidance pointing away from ultraprocessed foods requires a credible plan for affordability — because for millions of Americans, the cheapest calorie on the shelf is also the most processed one.