Protocol
Avoiding ultra-processed food
Graded on short-term energy intake and body weight over 1 to 8 weeks in controlled feeding trials: people ate roughly 500 kcal/day more on an ultra-processed diet than a minimally processed one with macronutrients matched, and gained weight, in an inpatient trial since replicated The same finding reproduced by a separate research group. A result seen once can be chance or bias; a replicated one is harder to explain away. in Japan and the United Kingdom.
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How this letter has changedLatest: October 2026 · Corrected.
The record said the Hall trial was 'confirmed by' Lane 2024 (PMID PubMed ID: the permanent number the US National Library of Medicine gives a published paper. Each one links to that paper's record on PubMed. 38418082), an umbrella review of observational studies that cannot confirm a trial or carry a grade. The randomized replications are now cited: Hamano 2024 (PMID 39267249) and Dicken 2025 (PMID 40760353). Sciarrillo 2024 (PMID 39163976) answers the no-washout objection. The nulls and limits are shown: Rego 2026 (PMID 41255123) and Aramburu 2024 (PMID 38988861). The description now says what the B covers, short-term intake and weight over 1 to 8 weeks. The replication search owed since October is closed. Letter unchanged.PMID 38418082 PMID 39267249 PMID 40760353 PMID 39163976 PMID 41255123 PMID 38988861
Every change to a letter on this site is dated and published. The full evidence log →
This page is about cutting back on ultra-processed food. In a tightly controlled hospital study, 20 adults ate about 500 more calories a day on an ultra-processed diet. The other diet was less processed, with the same balance of nutrients. On the ultra-processed diet, they also gained weight. Studies in Japan and England found the same direction. These studies lasted 1 to 8 weeks and looked only at eating and weight. Links to disease and deaths come from studies that only watched people.
Graded on short-term energy intake and body weight over 1 to 8 weeks in controlled feeding trials: people ate roughly 500 kcal/day more on an ultra-processed diet than a minimally processed one with macronutrients matched, and gained weight, in an inpatient trial since replicated in Japan and the United Kingdom. No randomized trial tests hard outcomes; the mortality and disease associations are observational and carry no grade.
Why this gradeThe reasoning, and what the grade does not cover.
Grade B on short-term energy intake and body weight. In an inpatient randomized crossover A trial design in which each participant receives both the treatment and the comparison, one after the other, and serves as their own control., 20 adults ate about 500 kcal/day more and gained weight on an ultra-processed diet matched for macronutrients (Hall et al., 2019; PMID 31105044); a crossover in Japan (Hamano et al., 2024; PMID 39267249) and an 8-week trial in England (Dicken et al., 2025; PMID 40760353) replicated the direction.
WHY NOT Aintake and weight over 1 to 8 weeks are surrogates.
WHAT THIS GRADE DOES NOT COVERdisease or mortality. Those associations are observational (for example Schnabel et al., 2019; PMID 30742202) and carry no letter here.
A grade describes the human evidence for a named use. It is not advice, and it is not a judgment on any individual prescription. How the letters are decided →
The evidence, in fullSeven papers, each linked to its PubMed record.
Hall et al. (Cell Metabolism, 2019; PMID 31105044): inpatient randomized crossover trial, 20 adults, ultra-processed diet raised energy intake about 500 kcal/day and body weight versus a matched minimally processed diet. Replicated: Hamano et al. (Diabetes Obes Metab, 2024; PMID 39267249), Japan, randomized crossover with a 2-week washout, 9 men, 1.1 kg more weight and 814 kcal/day more intake on ultra-processed food; Dicken et al. (Nature Medicine, 2025; PMID 40760353), England, 55 adults, two 8-week diets both following national guidelines, greater weight loss on minimally processed food (1.0 percent more, P = 0.024), funded by the Medical Research Council. The Hall crossover had no washout; Sciarrillo et al. (Am J Clin Nutr, 2024; PMID 39163976), a secondary analysis, found no diet-order effect in that trial. Against and limits: Rego et al. (Obesity, 2026; PMID 41255123), 27 young adults, a 2-week diet of 81 percent ultra-processed food did not change later ad libitum intake in the full sample; Aramburu et al. (Front Nutr, 2024; PMID 38988861), systematic review A review that searches for every study on a question using a method set in advance, then assesses them together. of 4 randomized trials, no significant effect on 30 of 42 outcomes, certainty low to moderate. Lane et al. (BMJ, 2024; PMID 38418082) is an umbrella review of observational meta-analyses A study that pools the numbers from several trials into one combined estimate.; it describes associations and carries no grade. Grade B: replicated randomized evidence on a surrogate (short-term intake and weight).
UPF consumption as a percentage of total dietary energy using the NOVA classification: a 24-hour dietary recall or food frequency questionnaire at baseline and 3 months quantifies the intervention. Weight, waist circumference, and hsCRP High-sensitivity C-reactive protein, a blood marker of low-grade inflammation. at 3 months. The HALL et al. NIH trial showed spontaneous caloric reduction averaging 500 kcal/day when UPFs were removed: Total energy intake if feasible.
Evidence notes: randomized trial
Endpoint The outcome a trial measures to decide whether the treatment worked, such as heart attacks, blood pressure or a symptom score. graded: Short-term energy intake and body weight (surrogate)
Last reviewed: July 2026
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How EBL searched for the trials (1 search)
The search that was run, what it returned, and what was left out and why, so the absence of evidence can be checked as well as its presence.
(ultra-processed[tiab] OR ultraprocessed[tiab]) AND (randomized controlled trial[pt] OR systematic review[pt]) AND humans[mesh]Grades move when new trials publish. A free monthly email lists every grade EBL moved, with the reason and the trial behind it: the sign-up is on the Evidence Log →