Key takeaways
- There is no official US definition of “ultra-processed food” yet. The FDA and USDA are working on one. Most research uses a Brazilian system called NOVA.
- In a small NIH trial, 20 adults ate about 508 more calories a day and gained weight on an ultra-processed diet than on an unprocessed one, even though the meals were matched on nutrients on paper.
- A 2024 review of 45 analyses (about 9.9 million people) found associations with higher risks of heart disease death, type 2 diabetes and common mental disorders, but the quality of evidence was rated low to very low for most findings.
- A UK government expert committee says the evidence is almost entirely observational and it is unclear whether processing itself or the nutrients in these foods is the cause.
This article is general health information, not medical or dietary advice.
What counts as “ultra-processed”?
The honest answer is that it depends on who you ask. The FDA says there is no uniform definition for the US food supply and that it is working with the USDA to develop one. In July 2025 the two agencies asked the public for data and ideas on what should be in the definition. The FDA says researchers have linked highly processed foods to health problems including cardiovascular disease, obesity and certain cancers, and notes an estimate that about 70% of the US food supply is made up of foods commonly considered ultra-processed.
Most studies use the NOVA system, developed in Brazil. The UK’s Scientific Advisory Committee on Nutrition (SACN) notes NOVA is one of several classification systems, that its categories “are very broad” and group together foods with different nutrition, and that NOVA doesn’t consider a food’s nutrient content.
The best experiment: the NIH feeding trial (Cell Metabolism, 2019)
Twenty adults stayed at the NIH Clinical Center for four weeks. They were randomly assigned to two weeks on an ultra-processed diet, then two weeks on an unprocessed diet, or the reverse. The meals were matched for calories as presented, energy density, macronutrients, sugar, sodium and fibre, and participants could eat as much or as little as they wanted.
- They ate 508 more calories a day on the ultra-processed diet.
- They gained 0.9 kg (about 2 pounds) on the ultra-processed diet and lost 0.9 kg on the unprocessed one, over two weeks each.
It’s a real randomized trial, which is rare in this field. But it was 20 people for four weeks, so it can’t tell us about long-term disease. The authors concluded that limiting ultra-processed foods “may be an effective strategy for obesity prevention and treatment.”
The big review: associations in about 9.9 million people (BMJ, 2024)
A BMJ umbrella review looked at 45 pooled analyses covering 9,888,373 people. It found direct associations between ultra-processed food and 32 of 45 health measures (71%). For the strongest category of evidence (“convincing”), higher intake was linked to:
- Cardiovascular disease death: risk ratio 1.50 (GRADE quality: very low).
- Type 2 diabetes: risk ratio 1.12 per unit increase (moderate quality).
- Anxiety (odds ratio 1.48) and common mental disorders (1.53), both low quality.
“Highly suggestive” evidence linked it to higher risk of dying from any cause (risk ratio 1.21, low quality). Notice the quality labels: most of these were low or very low under the review’s own rating system. These are associations from observational studies, which can’t prove cause.
The big picture claim: The Lancet series (2025)
A 2025 Lancet series paper argued that ultra-processed foods are displacing whole-food diets worldwide and that the pattern “increases the risk of multiple diet-related chronic diseases,” citing more than 100 prospective studies, trials and mechanistic studies, and concluding the evidence supports it as “a key driver” of chronic disease. It is a strong position and an influential one. Other experts are more cautious, as the next section shows.
The caution: what UK experts say
SACN’s 2023 review, which looked at the evidence on processed foods and health, found:
- “The available evidence is almost exclusively observational in nature.”
- “The majority of included studies used the NOVA classification system.”
- Inconsistent adjustment for other factors across reviews.
- It is unclear whether these foods are harmful because of processing itself or because many of them are high in calories, saturated fat, salt and sugar and low in fibre.
SACN’s recommended research includes good-quality randomized trials, long-term cohort studies, and studies of additives and processing methods.
What this means for your plate
The sources suggest a practical, low-drama approach:
- Don’t panic over single foods. The evidence is about overall diet patterns, and the definition is still being settled.
- Look at nutrition, not just “processed.” Because the cause is unclear, the nutrition label still helps. See our guide to reading a Nutrition Facts label.
- Eat more minimally processed foods where you can. This is our reading of the trial, not an official recommendation: the unprocessed diet led to lower calorie intake in that setting.
- Talk to a dietitian if you have a condition or specific goals.
Frequently asked questions
Is ultra-processed food definitely harmful? One small trial linked it to eating more and gaining weight, and large reviews link it to disease risk. But the review quality is mostly low, and UK experts say the evidence is almost all observational.
What does “ultra-processed” mean? There’s no US legal definition yet. Researchers mostly use the NOVA system from Brazil.
Is it the processing or the nutrients? Unknown, according to SACN.
What should I do? Focus on your overall diet and use nutrition labels. A dietitian can give personal advice.
Information checked on: November 13, 2026. Definitions and research are changing, so check current sources.
Sources
- Ultra-Processed Diets Cause Excess Calorie Intake and Weight Gain: An Inpatient Randomized Controlled Trial of Ad Libitum Food Intake. Cell Metabolism, 2019
- Ultra-processed food exposure and adverse health outcomes: umbrella review of epidemiological meta-analyses. BMJ, 2024
- Ultra-processed foods and human health: the main thesis and the evidence. The Lancet, 2025
- UK Scientific Advisory Committee on Nutrition, “SACN statement on processed foods and health: summary report” (July 11, 2023)
- US Food and Drug Administration, “Ultra-Processed Foods” (content current as of September 18, 2025)
Health note: this article is for general information and is not medical advice. Speak to a qualified health professional about your own situation.
