Adults with the highest intake of ultra-processed foods were 26 percent more likely to develop severe non-alcoholic fatty liver disease than those who ate the least, a large UK Biobank study has found.
The prospective analysis, published in The Journal of Nutrition, Health & Aging in September 2024, tracked 143,073 participants for a median of 10.5 years.
During follow-up, 1,445 people developed severe non-alcoholic fatty liver disease (NAFLD), a condition in which fat builds up in liver cells and can progress to scarring and cirrhosis.
Comparing the top and bottom quartiles of ultra-processed food intake, the fully adjusted hazard ratio was 1.26 (95% CI: 1.11 to 1.43). The team, led by Yi-Feng Zhang, used the NOVA classification and 24-hour dietary recalls to measure intake.
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A separate meta-analysis published in Frontiers in Nutrition on July 11, 2025, pooled 10 studies covering 513,440 participants and 20,637 NAFLD cases.
The highest ultra-processed food consumers had a 22 percent higher risk of NAFLD than the lowest (RR = 1.22, 95% CI: 1.14 to 1.31). Each 10 percent increase in the ultra-processed share of the diet raised risk by another 6 percent.
Why calories alone don't explain it
The UK Biobank finding held after researchers adjusted for body mass index. That matters. It weakens the argument that ultra-processed foods harm the liver simply because people who eat more of them tend to be heavier.
The association was slightly attenuated when BMI entered the model, the authors noted, but stayed statistically significant.
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Another UK Biobank analysis, published in the American Journal of Clinical Nutrition, tracked 173,889 adults for a median of 8.9 years.
The highest ultra-processed food quartile had a 43 percent higher risk of NAFLD (HR 1.43, 95% CI: 1.21 to 1.70) and a 50 percent higher risk of severe liver disease overall (HR 1.50, 95% CI: 1.19 to 1.90), compared with the lowest.
How ultra-processed foods may harm the liver
The 2025 meta-analysis authors mapped several plausible mechanisms. Ultra-processed foods pack in added sugars, saturated fat and salt while stripping out fiber, vitamins and minerals.
Common additives such as carrageenan and artificial sweeteners can alter gut bacteria and worsen insulin resistance, the state where the body's cells respond less effectively to insulin.
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High-temperature industrial processing also generates advanced glycation end products and acrylamide, compounds linked to inflammation and metabolic stress. Endocrine-disrupting chemicals from packaging, such as bisphenol A and phthalates, may nudge the liver toward fat storage.
What counts as ultra-processed
The NOVA system groups foods into four tiers by how much industrial processing they undergo. Ultra-processed items sit at the top tier. They are industrial formulations with colorings, emulsifiers, preservatives, artificial flavors or sweeteners.
Common examples are sugary drinks, packaged snacks and cookies, most breakfast cereals, ready meals and processed meats such as hot dogs and luncheon meats.
The category is a huge share of what Americans eat. A CDC National Center for Health Statistics data brief from August 2025 found U.S. adults got 53 percent of their daily calories from ultra-processed foods between 2021 and 2023.
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For children the figure was 62 percent. Top calorie sources included burgers and sandwiches, sweet baked goods, sweetened beverages and savory snacks.
Anyone worried about symptoms of fatty liver disease, such as persistent fatigue or discomfort in the upper right abdomen, should speak with a doctor.
Simple swaps that move the diet down the NOVA ladder include water in place of soda, whole fruit or unsalted nuts in place of packaged snacks, and plain oats in place of sugar-sweetened breakfast cereals.
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This article is made and published by Mie Hermansen, who may have used AI in the preparation.